Charged-particle-beam exposure device and charged-particle-beam exposure method

ABSTRACT

A method of exposing a wafer to a charged-particle beam by directing to the wafer the charged-particle beam deflected by a deflector includes the steps of arranging a plurality of first marks at different heights, focusing the charged-particle beam on each of the first marks by using a focus coil provided above the deflector, obtaining a focus distance for each of the first marks, obtaining deflection-efficiency-correction coefficients for each of the first marks, and using linear functions of the focus distance for approximating the deflection-efficiency-correction coefficients to obtain the deflection-efficiency-correction coefficients for an arbitrary value of the focus distance. A device for carrying out the method is also set forth.

This application is a division of application Ser. No. 08/634,410, filedApr. 18, 1996, now U.S. Pat. No. 5,757,015.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to charged-particle-beamexposure devices, and particularly relates to a charged-particle-beamexposure device which forms a pattern on a wafer by exposing the waferto charged particles.

2. Description of the Related Art

As the circuit density of semiconductor integrated circuits increases, afiner processing technique is required. Compared to the light exposuremethod widely used in the manufacturing of LSI chips, thecharged-particle exposure method has much superior characteristics interms of the resolution and the focus depth. With respect to theresolution, a processing limit of the photolithography method is about0.3 μm, while processing as fine as 0.1 μm can be achieved in thecharged-particle-beam exposure method.

However, the charged-particle-beam exposure method is inferior comparedto the light exposure method in terms of an exposure positioningaccuracy, an overlay accuracy, and a field stitching accuracy. Becauseof this, the charged-particle-beam exposure method is not widely used inthe field for manufacturing purposes of LSI chips.

The charged-particle-beam exposure device has a smaller area to be ableto be exposed at one time, compared to a light exposure device such as astepper. (This area is called a deflection field hereinafter.) Thus, inorder to expose one LSI chip, stage movement is required to successivelyshift the deflection field on the LSI chip. In doing so, if theconnecting precision across borders of the deflection fields is low,severance of wires and/or short-circuits are generated which greatlydegrades the yield of the chips.

In order to improve the yield, the connecting precision at the fieldborders must be enhanced, which requires a higher precision of thedeflection of the charged-particle beam. In the charged-particle-beamexposure device, the charged-particle beam is generally deflected by amagnetic field generated by coils. The coils include two systems forx-direction deflection and for y-direction deflection. Separate currentsare applied to these two systems to deflect the beam in the x directionand the y direction independently. Unfortunately, the amount of beamdeflection is not in proportion to the amount of current applied to thedeflection coils, but is represented as a complex function of thecurrent amount.

In order to deflect the beam with a high precision, the amount of thecurrent applied to the deflector must be corrected. There are two typesof corrections. One is a distortion correction for establishing a linearrelation between the input and the deflection amount, and the other is adeflection-efficiency correction for correcting coefficients for linearfactors. The distortion correction is a time consuming process since itrequires data collection at various points within the field. However,the data needs to be collected only one time since a time variation ofthe distortion is small. On the other hand, correction coefficients canbe obtained in a short period of time for the deflection-efficiencycorrection. However, the deflection-efficiency-correction coefficientsmust be frequently obtained because the deflection efficiency variesover time due to a change in thermal distribution of the deflector, etc.

In order to calibrate the deflection field, coordinates of the deflectorare generally matched with coordinates of the stage, whose measure andorthogonality are guaranteed through the laser-interferometer system. Inorder to measure the coordinates of the deflector, an actual position ofthe charged-particle beam must be obtained by directing the beam to markpositions on a wafer and detecting reflected charged particles.

FIG. 1A is an illustrative drawing for explaining a method of detectingmark positions through the charged-particle-beam scan. As shown in FIG.1A, the charged-particle beam is scanned by the deflector over a mark306 formed as a groove in a reference chip 305. Reflection detectors 300and 301, symmetrically arranged with respect to the axis of the beamoptical system, detect reflected charged particles. Outputs of thedetectors are added by the adder 302. A signal after the addition issuccessively obtained in synchronism with the scan of the deflector,providing a reflection signal form to be analyzed. When such a processis conducted by using the position-detection mark 306 as shown in FIG.1A, a reflection signal form as shown in FIG. 1B is obtained. Thereflection signal form obtained in this manner is analyzed by ananalyzing device 303 to detect a center position of the mark. A resultof the analysis is sent from the analyzing device 303 to acontrol-purpose computer 304, which uses the result in processes such asa correction of the beam. In general, a groove (dent) formed in a wafer(silicon) is used as a mark.

The detection of the position mark described above is conducted atvarious points by shifting the mark on a wafer through stage movement.In this manner, the deflection-efficiency-correction coefficients forcorrecting the linear factors and a distortion map of the deflector forthe distortion correction are obtained.

In the mark-position-detection method described above, the detected markpositions contain errors. This is because a relative position of themark with respect to the reflection detectors changes when the mark isdetected at various points.

When the mark is detected at various points, an angle at which chargedparticles are reflected by the mark toward a reflection detector variesdepending on a relative position of the mark with respect to thereflection detector. When reflected charged particles are detected in aconfiguration as shown in FIG. 2A, signal forms as shown in FIG. 2B areobtained. As shown in figures, a reflection signal having a symmetricform without a distortion can be obtained when the mark is positioned atan equal distance from the two reflection detectors. When the mark ispositioned at other locations, however, a reflection signal form havingan asymmetry is obtained. This is because the angle of the reflection isdifferent for the different reflection detectors.

In addition to the problems of errors regarding the mark-positiondetection, there is a problem concerning the focusing of thecharged-particle beam in the charged-particle-beam exposure device.

FIG. 3 is an illustrative drawing showing a configuration for thefocusing of the beam in the related-art charged-particle-beam exposuredevice. As shown in FIG. 3, an optical system 310, using a type of lightnot affecting a resist, is provided between a wafer and acharged-particle lens. The optical system 310 includes a light source311 and a light detector 312. When the wafer is exposed to thecharged-particle beam, the light source 311 illuminates light on thewafer, and the light detector 312 detects light reflected from the waferto measure the height of an exposed surface. Based on the height of theexposed surface, a focusing distance of the charged-particle lens ischanged.

Such a related-art charged-particle-beam exposure device has suchproblems as:

a) when the focusing distance of the reflection path is changed, thedeflection path of the charged-particle beam is affected to cause adisplacement of the beam position on the wafer surface; and

b) since structures under the exposed surface have complex patterns in aLSI device, light reflected from these patterns has an adverse effect ofcausing errors in the detection of the height.

The problem a) will be described below. In the charged-particle-beamexposure device, deflection coordinates X=(X, Y), having an origin atthe axis of the beam optical system, are entered into a correctioncircuit to obtain corrected deflection coordinates X'=(X', Y').

    X'=Gx•X+Rx•Y+Dx(X, Y)                          (1)

    Y'=Ry•X+Gy•Y+Dy(X, Y)                          (2)

Here, G=(Gx, Gy) are correction coefficients concerning the gain, R=(Rx,Ry) are correction coefficients concerning the rotation, and D=(Dx, Dy)are distortions of higher orders other than the gain and the rotation.In the charged-particle-beam exposure device, a current proportional tothe corrected deflection coordinates X'=(X', Y') is applied to thedeflector to direct the beam at a desired position X=(X, Y) on thewafer.

When the focusing distance of the lens is changed, the beam cannot bedirected to the desired position X. Thus, G, R, and the distortion D(X)must be changed in accordance with the change in the focusing distance.

In order to direct the charged-particle beam at a desired position X ona wafer surface having a given focusing distance (height) f, thecorrection coefficient G, the correction coefficient R, and thedistortion D(X) at various heights f must be measured. In this manner,correction coefficients having the height as a variable, i.e., thecorrection coefficient G(f), the correction coefficient R(f), and thedistortion D(X, f), are obtained. Taking these measurements, however,increases the time for adjusting the beam deflection, and leads to thecorrection circuit being more complex.

The problem b) will be described below. Instead of using the opticalsystem of FIG. 3 to take the real-time measurement of the height at thetime of exposure, reference marks provided on each chip to be exposedcan be used for the measurement of the height. Namely, the height ofeach chip is measured by using the reference marks arranged at fourcorners of the chip to carry out the focusing and the correction. Sincethe reference marks have the same predetermined structure irrespectiveof the chips, the use of such marks allows an easy measurement of theheight. In this method, however, the reference marks at the four cornersmust be detected for the measurement of the height each time theexposure is made. Thus, the processing time is increased. Also, the sameas the method of measuring the height in real time, errors in themeasurements lead to deviation of the focusing. Further, in case thatthe heights of the reference marks are not measured for some reason, thefocusing on the chip surface cannot be carried out.

In addition to the problems of the mark-position-detection errors andthe focusing described above, there is another problem concerning theaccuracy of exposed patterns in the charged-particle-beam exposuredevice.

FIG. 4 is an illustrative drawing for explaining a process of thecharged-particle exposure on a wafer. The wafer is divided into areas ofa 20-mm square. Here, an IC chip pattern or the like exposed on thewafer generally has a size ranging from a 5-mm square to a 20-mm square.When the IC chips are small, four to nine chips are included together inone area. When the IC chips are large, one chip is included in one area.At the time of exposure, the corrections of the gain, the rotation, thedistortion are carried out for each area on the wafer. In general, theexposure data is set for each area unit.

The charged-particle-beam exposure device generally has a main deflectorcapable of deflecting the beam within a large region and a sub-deflectorcapable of deflecting the beam at high speed within a small region. Themain deflector first directs the beam at a predetermined desiredposition, and, then, the sub-deflector draws a pattern around thepredetermined desired position. In FIG. 4, one area is divided intocells (hereinafter called cell fields), in each of which the maindeflector can deflect the beam. When a center point of one cell field isaligned with the axis of the beam optical system, the main deflector candeflect the beam over this cell field. Each cell field has a size of a1-to-2 mm square. Thus, one area is comprised of about 100 cell fields.Further, the cell field is divided into sub-fields having a size ofabout a 100-μm square. The sub-deflector can deflect the beam within thesub-field.

The measurements of the deflector-correction data prior to the exposureare conducted within the cell field. Based on the correction data, thecorrection coefficients of the main-deflector coordinates, thesub-deflector coordinates, and the distortion relative to the stagecoordinates are determined. Normally, the correction coefficients of themain deflector are set for each area, and the correction coefficients ofthe sub-deflector are set for each cell.

The exposure is conducted for a frame, which is a region comprised of aplurality of cell fields arranged in a line. Since the width of theframe is the same as that of a cell field, the beam can be deflected bythe main deflector within the width of the frame. For the exposure alonga longitudinal direction of the frame, the wafer is successively shiftedin the longitudinal direction of the frame through the stage movement.Namely, for the exposure in a transverse direction of the frame, themain deflector deflects the beam for positioning thereof, and thesub-deflector is used for the exposure. For the exposure in thelongitudinal direction of the frame, the wafer is successively moved bythe stage. After a completion of a one frame exposure, the stage takes aU turn to move the wafer in an opposite direction.

In general, the accuracy of the exposed pattern must be within a 10%tolerance of the exposed pattern. For example, when a 0.15-μm pattern isexposed, the accuracy must be higher than 0.015 μm. In order to achievethis accuracy, the beam correction described above must be preciselyconducted. Moreover, there is an effect of a thermal drift of thedeflectors during the wafer exposure. Thus, the correction coefficientsof the main and sub-deflectors obtained prior to the exposure must beupdated during the exposure.

In order to achieve a high precision, therefore, the updating of thecorrection coefficients must be conducted for each cell or morefrequently. The correction coefficients stored in a correction operationcircuit must be updated during a break of the exposure such as betweenthe cells or between the sub-fields. Unfortunately, the updating of thecorrection coefficients is a time consuming process. Thus, frequentupdating leads to an increase in exposure time, thereby degrading theperformance.

In order to obviate this problem, all the correction coefficients may becalculated and transferred to the correction operation circuit during atime period from a data collection prior to the exposure to thebeginning of the exposure. Assuming that 40 coefficients are requiredfor one cell, for example, these 40 coefficients must be calculated forabout 4000 points when a 6-inch wafer is used. This means that 1-to-5seconds are required for the calculation. The data transfer also needs asimilar time period. Furthermore, a large-volume memory for storing thecorrection coefficients is needed in the correction operation circuit.Also, when the correction coefficients are updated during the exposure,all the correction coefficients need to be rewritten after thecollection of the correction data.

As described above, there are problems of the mark-position-detectionerrors, the focusing of the beam, and the setting of the correctioncoefficients in the related-art charged-particle-beam exposure device. Acombination of these problems leads to defects of the generated exposurepattern. When counter measures are taken to avoid these defects, thetime required for the adjustment and the exposure is increased, and thedevice becomes undesirably complex.

Accordingly, there is a need for a device and a method of exposing thecharged-particle beam which can create accurate exposure patterns withhigh productivity.

Also, there is a need for a device and a method of exposing thecharged-particle beam which can achieve high-accuracy beam focusing andhigh-accuracy beam positioning without requiring a long time forbeam-deflection adjustment.

Also, there is a need for a device and a method of exposing thecharged-particle beam which can accurately detect a mark position.

Also, there is a need for a device and a method of exposing thecharged-particle beam which can use correction coefficients provided forsmall units of areas without sacrificing the exposure processing time.

SUMMARY OF THE INVENTION

It is general object of the present invention to provide acharged-particle-beam exposure device which can satisfy the needsdescribed above.

It is another and more specific object of the present invention toprovide a device and a method of exposing the charged-particle beamwhich can create accurate exposure patterns with high productivity.

It is still another object of the present invention to provide a deviceand a method of exposing the charged-particle beam which can achievehigh-accuracy beam focusing and high-accuracy beam positioning withoutrequiring a long time for beam-deflection adjustment.

In order to achieve the above objects according to the presentinvention, a method of exposing a wafer to a charged-particle beam bydirecting to the wafer the charged-particle beam deflected by adeflector includes the steps of arranging a plurality of first marks atdifferent heights, focusing the charged-particle beam on each of thefirst marks by using a focus coil provided above the deflector,obtaining a focus distance for each of the first marks, obtainingdeflection-efficiency-correction coefficients for each of the firstmarks, and using linear functions of the focus distance forapproximating the deflection-efficiency-correction coefficients toobtain the deflection-efficiency-correction coefficients for anarbitrary value of the focus distance.

In order to achieve the same objects according to the present invention,a device for exposing a wafer to a charged-particle beam by directing tothe wafer the charged-particle beam deflected by a deflector includes afocus coil provided above the deflector, a unit for arranging aplurality of first marks at different heights, a unit for focusing thecharged-particle beam on each of the first marks by using the focuscoil, a unit for obtaining a focus distance for each of the first marks,a unit for obtaining deflection-efficiency-correction coefficients foreach of the first marks, and a unit for obtaining thedeflection-efficiency-correction coefficients for an arbitrary value ofthe focus distance by using linear functions of the focus distance forapproximating to the deflection-efficiency-correction coefficients.

According to the method and the device described above, thedeflection-efficiency-correction coefficients for any focus distance areobtained by simply measuring the deflection-efficiency-correctioncoefficients and the focus distances for the marks arranged at differentheights. Thus, the method and the device can achieve high-accuracy beampositioning without requiring a long time for beam-deflectionadjustment.

The above method further includes the steps of positioning a second markat a center of an optical system of the charged-particle beam, obtaininga first -position and a first focus distance of the second mark byfocusing the charged-particle beam on the second mark through the focuscoil, obtaining a second position of the second mark after shifting thesecond mark to a second focus distance different from the first focusdistance, and using a linear function of the focus distance forapproximating to a displacement of the charged-particle beam based onthe first position, the second position, the first focus position, andthe second focus position to obtain the displacement for an arbitraryvalue of the focus distance, obtaining a reference focus distance foreach of the reference marks provided on the wafer by focusing thecharged-particle beam on each of the reference marks through the focuscoil, using a function of coordinates on the wafer for approximating thereference focus distance through a least square method to obtain anexposure focus distance for an arbitrary point on the wafer, andcarrying out positioning and exposure of the wafer by using the exposurefocus distance, the deflection-efficiency-correction coefficients forthe exposure focus distance, and the displacement for the exposure focusdistance.

The above device further includes a unit for positioning a second markat a center of an optical system of the charged-particle beam, a unitfor obtaining a first position and a first focus distance of the secondmark by focusing the charged-particle beam on the second mark throughthe focus coil, a unit for obtaining a second position of the secondmark after shifting the second mark to a second focus distance differentfrom the first focus distance, a unit for obtaining a displacement ofthe charged-particle beam for an arbitrary value of the focus distanceby using a linear function of the focus distance for approximating tothe displacement of the charged-particle beam based on the firstposition, the second position, the first focus position, and the secondfocus position, a reference-focus-distance obtaining unit for obtaininga reference focus distance for each of reference marks provided on thewafer by focusing the charged-particle beam on each of the referencemarks through the focus coil, a unit for obtaining an exposure focusdistance for an arbitrary point on the wafer by using a function ofcoordinates on the wafer for approximating the reference focus distancethrough a least square method, and a unit for carrying out positioningand exposure of the wafer by using the exposure focus distance, thedeflection-efficiency-correction coefficients for the exposure focusdistance, and the displacement for the exposure focus distance.

According to the method and the device described above, the displacementof the charged-particle beam is approximated to by the linear functionof the focus distance, and, also, the exposure focus distance on thesurface of the wafer is approximated by the function of coordinates onthe wafer. Thus, higher orders of the deflection distortion dependent onthe height need not be measured, so that the time required for theadjustment of the entire system can be shortened. Also, failure to focusthe beam at the time of exposure is avoided so as to greatly reduce theblurring of patterns.

It is still another object of the present invention to provide a deviceand a method of exposing the charged-particle beam which can accuratelydetect a mark position.

In order to achieve the above object according to the present invention,a method of exposing a wafer to a charged-particle beam by directing tothe wafer the charged-particle beam deflected by a deflector, the methodcomprising the steps of positioning a position-detection mark atpredetermined locations, the position-detection mark including heavymetal buried in a substrate which has lower reflectivity than the heavymetal, the heavy metal and the substrate having the same flat surface,and detecting positions of the position-detection mark by using thecharged-particle beam.

In order to achieve the same object according to the present invention,a device for exposing a wafer to a charged-particle beam by directing tothe wafer the charged-particle beam deflected by a deflector, the devicecomprising, a wafer stage carrying the wafer to move the wafer, and aposition-detection mark provided on the wafer stage, the positiondetection mark including heavy metal buried in a substrate which haslower reflectivity than the heavy metal, the heavy metal and thesubstrate having the same flat surface.

According to the method and the device described above, the positiondetection mark is formed from the heavy metal and the substrate, so thata difference in the reflection intensity between the heavy metal and thesubstrate can be detected at a time of mark detection. Thus, the use ofsuch a position detection mark eliminates errors in the mark-positiondetection.

It is a further object of the present invention to provide a device anda method of exposing the charged-particle beam which can use correctioncoefficients provided for small units of areas without sacrificing theexposure processing time.

In order to achieve the above object according to the present invention,a device exposes a wafer to a charged-particle beam deflected by adeflector, in which each of the frames defined on the wafer issuccessively exposed to the charged-particle beam while the wafer iscontinuously shifted through stage movement. The device includes anobtaining unit for obtaining data regarding correction of the deflectorin order to correct positioning of the charged-particle beam for aprecise exposure of the wafer, a data storing unit for storing the data,a coefficient calculating unit for calculating, based on the data storedin the data storing unit, correction coefficients of the correction fora first frame of the frames prior to an exposure, and for calculating,based on the data stored in the data storing unit, the correctioncoefficients of the correction for a n+1-th (n:integer) frame of theframes during a period when a n-th frame of the frames is being exposed,a coefficient storing unit for storing the correction coefficients, anda correction calculating unit for correcting the charged-particle beamto expose one of the frames based on the correction coefficientscalculated while an immediately previous one of the frames is beingexposed.

In order to achieve the same object according to the present invention,a method exposes a wafer to a charged-particle beam in acharged-particle beam exposure device having a main deflector deflectingthe charged-particle beam within a first area and a sub-deflectordeflecting the charged-particle beam within a second area smaller thanthe first area, an exposed surface of the wafer being divided intoareas, each of the areas being divided into cell fields, each of cellfields corresponding to the first area and being divided intosub-fields, each of the sub-fields corresponding to the second area, thecell fields being arranged in a plurality of lines defining frames onthe wafer, each of the frames being successively exposed to thecharged-particle beam by moving the wafer through stage movement. Themethod includes the steps of obtaining data regarding corrections of themain deflector and the sub-deflector prior to an exposure of the waferin order to correct positioning of the charged-particle beam for aprecise exposure of the wafer, calculating correction coefficients ofthe corrections for a first frame of the frames based on the data priorto the exposure of the wafer, calculating the correction coefficientsfor a given frame of the frames based on the data while a frameimmediately before the given frame is being exposed, and correcting thecharged-particle beam to expose one of the frames based on thecorrection coefficients calculated while a frame immediately before theone of the frames is being exposed.

According to the method and the device, when densely provided complexcorrection coefficients are set in the device for enhancement ofexposure precision, the calculation and storage of the correctioncoefficients are carried out in parallel with other processes requiredfor the exposure. Therefore, a large amount of calculation is carriedout, and the correction coefficients are set, without increasing theprocessing time for the exposure. That is, high-speed processing thesame as the prior-art device can be achieved. Furthermore, since thecorrection coefficients for only two frames are stored, a large volumememory is not necessary for the storage of the correction coefficients.

Other objects and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustrative drawing for explaining a method and a devicefor detecting a mark position through charged-particle-beam scan;

FIG. 1B is an illustrative drawing showing a signal form for detecting amark position obtained by the device of FIG. 1A;

FIGS. 2A and 2B are illustrative drawings for explaining asymmetryobserved in the signal form when the mark position is detected;

FIG. 3 is an illustrative drawing showing a configuration for thefocusing of the beam in a related-art charged-particle-beam exposuredevice;

FIG. 4 is an illustrative drawing for explaining a process of thecharged-particle exposure on a wafer;

FIG. 5 is an illustrative drawing showing a charged-particle-beamexposure device using a contrast-detection-type mark according to afirst principle of the present invention;

FIGS. 6A and 6B are illustrative drawings showing examples of thecontrast-detection-type mark formed in a reference chip;

FIG. 7 is a flowchart of a process of exposing a wafer in thecharged-particle-beam exposure device of FIG. 5 according to a firstembodiment of the present invention;

FIG. 8 is a flowchart of another process of exposing the wafer in thecharged-particle-beam exposure device of FIG. 5 according to a secondembodiment of the present invention;

FIG. 9 is an illustrative drawing of a charged-particle-beam exposuredevice according to a first embodiment of the second principle;

FIG. 10 is a flowchart of a process of obtainingdeflection-efficiency-correction coefficients as well as a displacementby using the device of FIG. 9;

FIGS. 11A through 11C are illustrative drawing showing chips and marksused in the process of FIG. 10;

FIG. 12 is a flowchart of an exposure process for a wafer by using thedevice of FIG. 9;

FIGS. 13A and 13B are illustrative drawings for explaining a method ofdetecting a just focus value of the charged-particle beam;

FIG. 14 is an illustrative drawing of a charged-particle-beam exposuredevice according to a second embodiment of the second principle;

FIG. 15 is a block diagram of an exemplary charged-particle-beamexposure device for conducting an exposure process according to a thirdprinciple of the present invention;

FIG. 16 is a block diagram of a correction-coefficient calculating andsetting unit according to a first embodiment of the third principle;

FIG. 17 is a block diagram of a coefficient storing unit according to asecond embodiment of the third principle;

FIG. 18 is a block diagram showing an example in which a dual-portmemory is used as frame-coefficient storing units of FIG. 17;

FIG. 19 is an illustrative drawing showing portions in one area whereframe exposures begin and end;

FIG. 20 is a block diagram of a portion for controlling the updating ofcell-correction coefficients and area-correction coefficients accordingto a third embodiment of the third principle of the present invention;

FIG. 21 is a block diagram of a variation of the third embodiment of thethird principle;

FIG. 22 is a table showing an example of a correction-coefficientpattern set by a correction-coefficient-pattern storing unit of FIG. 21;

FIG. 23A is a circuit diagram of an example of a dual-port memorycontrolled by the configuration of FIG. 17;

FIG. 23B is a chart showing data to be stored in the dual-port memory ofFIG. 23A;

FIG. 24 is an illustrative drawing showing a first related-art method ofobtaining a map of deflection-efficiency-correction coefficients of asub-deflector;

FIG. 25 is an illustrative drawing showing a second related-art methodof obtaining a map of deflection-efficiency-correction coefficients ofthe sub-deflector;

FIG. 26 is an illustrative drawing showing a fourth principle of thepresent invention;

FIG. 27 is an illustrative drawing showing a fifth principle of thepresent invention;

FIG. 28 is a block diagram of an exemplary charged-particle-beamexposure device carrying out a deflection-efficiency correctionaccording to the fourth and fifth principles of the present invention;

FIG. 29 is an illustrative drawing showing a mark-position detectingportion of a charged-particle-beam exposure device of FIG. 28;

FIG. 30 is an illustrative drawing showing a reference chip providedwith four position-detection marks according to the fourth principle ofthe present invention;

FIG. 31 is a flowchart of a process of correcting a deflectionefficiency of a sub-deflector of FIG. 28 according to a first embodimentof the fourth principle;

FIG. 32 is an illustrative drawing for explaining calculations ofcorrection coefficients;

FIG. 33 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector of FIG. 28 according to a secondembodiment of the fourth principle;

FIG. 34 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector of FIG. 28 according to a thirdembodiment of the fourth principle;

FIG. 35 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector of FIG. 28 according to an embodiment ofthe fifth principle;

FIG. 36 is an illustrative drawing showing a configuration of an exampleof a charged-particle-beam exposure device using a block exposuretechnique;

FIG. 37 is an illustrative drawing showing an example of a block mask ofFIG. 36;

FIG. 38 is a block diagram of an exemplary driving unit of a maindeflector of FIG. 36;

FIGS. 39A through 39C are time charts showing signals observed atvarious points of FIG. 38;

FIG. 40 is an block diagram of a main part of a charged-particle-beamexposure device according to a first embodiment of a sixth principle ofthe present invention;

FIGS. 41A through 41D are time charts showing signals observed atvarious points of FIG. 40;

FIG. 42 is a block diagram of a main part of a charged-particle-beamexposure device according to a second embodiment of the sixth principleof the present invention;

FIG. 43 is a block diagram of an example of a data-timing-adjustmentcircuit of FIG. 42 shown with memories;

FIG. 44A is a time chart showing a clock provided from a clock unit ofFIG. 36 to a digital-to-analog converter and a clock generating circuitof FIG. 42;

FIG. 44B is a time chart showing an output signal observed at a node Dof FIG. 42 when a pulse generating circuit of FIG. 42 is not provided;

FIG. 44C is a time chart showing a clock provided from the clockgenerating circuit to a DAC of FIG. 42;

FIG. 44D is a time chart showing a correction pulse signal output froman IV converter of FIG. 42;

FIGS. 45A and 45B are time charts showing output voltages obtainedthrough a simulation;

FIG. 46 is a flowchart of a process of obtaining optimal pulseparameters;

FIG. 47 is a block diagram of a main part of a charged-particle-beamexposure device according to a third embodiment of the sixth principleof the present invention;

FIG. 48 is a flowchart of a process of obtaining the optimal pulseparameters according to the third embodiment of the sixth principle;

FIG. 49 is a block diagram of a main part of a charged-particle-beamexposure device according to a fourth embodiment of the sixth principleof the present invention;

FIG. 50 is a flowchart of a process of obtaining the optimal pulseparameters according to the fourth embodiment of the sixth principle;

FIGS. 51A and 51B are circuit diagrams showing configurations of thedynamic-mask stigmator DS of FIG. 36;

FIGS. 52A through 52D are charts showing the ringing of an output signalof an amplifier of FIG. 51A for various turn numbers of the coils LX1through LX4 of FIG. 51A;

FIG. 53 is a circuit diagram of the dynamic-mask-focus coil DF of FIG.36;

FIG. 54 is a circuit diagram of a main part of a charged-particle-beamexposure device according to a first embodiment of a seventh principle;

FIG. 55 is a chart showing a variation in a current density of theelectron beam passing through a round aperture of FIG. 36 when aposition of the electron beam is displaced by a drift in an output ofamplifiers;

FIG. 56 is a chart showing the drift in the output of the amplifier;

FIG. 57 is an illustrative drawing showing an example of a configurationof stigmator-coil portions of FIG. 54 when six are provided;

FIG. 58 is a circuit diagram of a main part of a charged-particle-beamexposure device according to a second embodiment of the seventhprinciple;

FIG. 59 is a chart showing a variation in the current density of theelectron beam passing through the round aperture when a position of theelectron beam is displaced by a drift in an output of amplifiers;

FIGS. 60A and 60B are illustrative drawings showing an example of aconfiguration of the focus-coil portions of FIG. 58 when five areprovided;

FIG. 61 is an illustrative drawing showing a configuration of acharged-particle-beam exposure device of the related art using a stencilmask;

FIG. 62 is an illustrative drawing showing a configuration of anothercharged-particle-beam exposure device of the related art;

FIG. 63 is a chart for showing a temporal change in a driving voltage ofdeflectors of FIG. 61 and FIG. 62 and for showing a settling time of thedeflectors;

FIG. 64 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a first embodiment ofthe eighth principle of the present invention;

FIG. 65 is an illustrative drawing showing a configuration of thedeflectors of FIG. 64;

FIGS. 66A and 66B are illustrative drawings for explaining trajectoriesof the charged-particle beam deflected by the deflectors;

FIGS. 67A through 67C are illustrative drawings showing an extent of thecharged-particle beam passing through electromagnetic lenses of FIG. 64with an enlargement of this extent in a direction perpendicular to abeam axis;

FIG. 68 is a flowchart of a process of determining focusing A1 tocorrect a position of a cross-over image in FIG. 64;

FIG. 69 is a flowchart of a process of obtaining desirable focusing Land an optimal value of a ratio in FIG. 64;

FIG. 70 is a chart showing a settling time shortened by a correctionprocess;

FIG. 71 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a second embodimentof the eighth principle of the present invention;

FIG. 72 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a third embodiment ofthe eighth principle of the present invention;

FIGS. 73A and 73B are illustrative drawings for explaining trajectoriesof the charged-particle beam deflected by deflectors of FIG. 72;

FIG. 74 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a fourth embodimentof the eighth principle of the present invention;

FIG. 75 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a fifth embodiment ofthe eighth principle of the present invention;

FIG. 76A is a chart for explaining a relation between a difference dVand a settling time of VM1 in FIG. 75;

FIG. 76B is a chart for explaining a relation between a difference dI0and a settling time of I in FIG. 75;

FIG. 76C is a chart showing a change of a voltage VS1 and a settlingtime of VS1 in FIG. 75; and

FIG. 76D is a chart showing an example of a correction value D3 forgiven pattern-selection data D1 in FIG. 75.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, principles and embodiments of the present inventionwill be described with reference to the accompanying drawings.

A first principle of the present invention will be described below. Thefirst principle is concerned with a device and a method of exposing,using a charged-particle beam which can accurately detect a markposition for the purposes of beam correction and beam positioning.

The first principle of the present invention uses a mark of buried heavymetal instead of a dent mark. When the dent mark is used, chargedparticles reflected by the dent with a strong reflection in a certaindirection are detected. Thus, depending on the detector's positionrelative to the dent mark, the detector may detect a strong reflectionor may detect a weak reflection. Accordingly, if the detector's relativeposition to the mark is different, a magnitude and a profile of thedetected reflection signal will be different. As a result, when a dentmark is used, the detected reflection signal is asymmetrically deformedunless the detectors are arranged symmetrically with respect to themark.

For a mark defined by a buried heavy metal according to the firstprinciple of the present invention, a mechanism of detecting the mark isprincipally different from that of the dent mark (hereinafter called anedge-detection-type mark). For the mark of the first principle, adifference in the reflection intensity between the heavy metal and thebackground (silicon) is detected. Namely, a contrast in the reflectionintensity is detected for the mark of the first principle. Hereinafter,the mark utilizing a difference in the reflection intensity is called acontrast-detection-type mark.

According to the first principle, the use of the contrast-detection-typemark eliminates errors in the mark-position detection.

FIG. 5 is an illustrative drawing showing a charged-particle-beamexposure device 10 using the contrast-detection-type mark. Thecharged-particle-beam exposure device 10 includes acharged-particle-beam generator 11, a deflector 12, reflection detectors13 and 14, an adder 15, a signal analyzing unit 16, a XY stage 17, and awafer holder 18. The wafer holder 18 includes a reference chip 19 and awafer 20. Each of the reference chip 19 and the wafer 20 includes acontrast-detection-type mark 21 and positioning marks 22. Thecharged-particle-beam exposure device 10 also includes a control unit(not shown) to control the charged-particle-beam generator 11, thedeflector 12, the signal analyzing unit 16, the XY stage 17, etc.

FIGS. 6A and 6B are illustrative drawings showing examples of thecontrast-detection-type mark 21 formed in the reference chip 19. Asshown in FIGS. 6A and 6B, the contrast-detection-type mark 21 is formedby burying heavy metal 24 such as Au, Ta, W, etc., in a substrate 23such as silicon. A surface of the reference chip 19 can be made smoothlyflat within a 0.1-μm accuracy by using the CMP (chemical mechanicalpolishing) method or the like. The CMP method is a well-known mechanicalpolishing method using a chemical polishing substance, and a descriptionthereof will be omitted.

As shown in FIG. 5, a charged-particle beam emitted from thecharged-particle-beam generator 11 is deflected by the deflector 12, andis directed to the reference chip 19 or to the wafer 20. At the time ofobtaining the distortion map and the deflection-correction coefficients,the beam is scanned over the contrast-detection-type mark 21 of thereference chip 19. The reflection detectors 13 and 14 symmetricallyarranged with respect to the axis of the beam optical system detectreflected charged particles, and the adder 15 adds outputs of thedetectors. A detected reflection signal after the addition is measuredin synchronism with the scan of the deflector, and, then, is analyzed bythe signal analyzing unit 16 to detect a center position of the mark.The contrast-detection-type mark 21 is successively positioned atpredetermined locations by the XY stage 17. Thus, errors of themark-position detections by using the deflector 12 can be known, basedon the coordinates of the XY stage 17.

The mark-position detection described above is carried out for variouspositions of the mark by successively shifting thecontrast-detection-type mark 21 through the XY stage 17. In this manner,the distortion map and the deflection-efficiency-correction coefficientsof the deflector 12 are obtained.

Since an exposure stage comes immediately after the growth of a layer tobe patterned in the LSI process, most of the positioning marks 22 on thewafer 20 are edge-detection-type marks. In order to position the wafer20, therefore, the positioning marks 22 of the edge-detection type aresuccessively positioned at a center of the beam optical system to bedetected. At the center of the beam optical system, position-detectionerrors are not generated even if the edge-detection-type mark is used.In this manner, the precise position and rotation of a pattern under asurface of the wafer 20 can be known.

FIG. 7 is a flowchart of a process of exposing the wafer 20 in thecharged-particle-beam exposure device 10 according to a first embodimentof the present invention.

At a step S1, a deflection-distortion map is obtained by using acontrast-detection-type mark on a reference chip to calibrate thecharged-particle beam.

At a step S2, marks on a wafer are scanned, and the beam is focused onthe wafer.

At a step S3, a plurality of positioning marks on the wafer aresuccessively positioned at a center of the field through the XY stage todetect the mark positions. In this manner, the precise position androtation of patterns under a surface of the wafer are known.

At a step S4, deflection-efficiency-correction coefficients are obtainedby using the contrast-detection-type mark.

At a step S5, a pattern is exposed on the wafer. This ends theprocedure.

When a long-time exposure is carried out, thedeflection-efficiency-correction coefficients may be repeatedly obtainedat the step S4 at predetermined time intervals to update thesecoefficients.

According to the procedure described above, the distortion map and thedeflection-efficiency-correction coefficients are obtained by using thecontrast-detection-type marks. Thus, the precise calibration andcorrection of the beam deflector can be carried out. Also, thepositioning marks are detected at the center of the field, i.e., at thecenter of the beam optical system, so that the precise positions androtations of the underneath patterns can be known. Therefore, exposedpatterns are precisely connected across field borders.

FIG. 8 is a flowchart of another process of exposing the wafer 20 in thecharged-particle-beam exposure device 10 according to a secondembodiment of the present invention. In the second embodiment, thepositioning marks of the edge-detection type on the wafer are used toobtain the deflection-efficiency-correction coefficients. Errors in thecorrection coefficients obtained by using the edge-detection-type markshave a repeatability in the same device if the marks have the samestructure. Thus, displacements commensurate with the errors measured inadvance can be added to the correction coefficients to obtain thecorrect correction coefficients.

At a step S11, a deflection-distortion map is obtained by using acontrast-detection-type mark on a reference chip to calibrate thecharged-particle beam.

At a step S12, marks on a wafer are scanned, and the beam is focused onthe wafer.

At a step S13, a plurality of positioning marks on the wafer aresuccessively positioned at a center of the field through a XY stage todetect the mark positions. In this manner, the precise position androtation of patterns under a surface of the wafer are known.

At a step S14, deflection-efficiency-correction coefficients areobtained by using the positioning marks on the wafer. Furthermore,displacements of the correction coefficients measured in advance areadded to the obtained deflection-efficiency-correction coefficients toobtain correct correction coefficients.

At a step S15, a pattern is exposed on the wafer. This ends theprocedure.

When a long-time exposure is carried out, thedeflection-efficiency-correction coefficients may be repeatedly obtainedat the step S14 at predetermined time intervals to update thesecoefficients.

According to the procedure described above, an accurate distortion mapis obtained by using the contrast-detection-type marks. Also, thedeflection-efficiency-correction coefficients are obtained by using thepositioning marks on the wafer, and the displacements measured inadvance are added to the obtained correction coefficients to obtaincorrect correction coefficients. Also, the positioning marks aredetected at the center of the field, i.e., at the center of the beamoptical system, so that the precise positions and rotations of theunderneath patterns can be known. Therefore, exposed patterns areprecisely connected across field borders.

According to the first and second embodiments of the first principle ofthe present invention, exposed patterns are precisely connected acrossfield borders even for underneath patterns having the positioning marksof the edge-detection type, such underneath patterns being used in thepatterning of semiconductor integrated circuits.

In the following, a second principle of the present invention will bedescribed below. The second principle is concerned with a device and amethod of exposing a charged-particle beam which can achievehigh-accuracy beam focusing and high-accuracy beam positioning withoutrequiring a long time for beam-deflection adjustment.

The second principle of the present invention uses thedeflection-correction coefficients varying in proportion to the focusingdistance after focusing the beam by a lens (focus coil) provided abovethe deflector.

In order to focus the beam on a wafer surface at different heightswithout greatly changing the deflected-beam path, a lens (focus coil)provided above the main and sub-deflectors must be used. When the beamis focused in this manner, the deflected-beam path is not affected bythe focusing of the beam. However, the deflected beam is not incident onthe wafer surface at a normal angle. Therefore, when the height of thewafer surface is varied, a position of the deflected-beam path on thewafer surface is changed even though the deflected beam remains on thesame path.

In this case, a displacement of the position is proportional to a changein the height and the amount of the deflection. Thus, it is sufficientto change the coefficients G and R in proportion to the height f.

    G(f)=g.sub.0 +g.sub.1 •f                             (3)

    R(f)=r.sub.0 +r.sub.1 •f                             (4)

Here, the distortion D(X) is not dependent on the height f.

When a center axis of the focus coil is displaced relative to the axisof the beam, the beam is deflected by the excitation of the focus coil,so that the deflection field on the wafer surface is displaced in itsentirety. When the displacement of the center axis is small, however, anangle of the beam deflection is proportional to the focus value. Thus,the displacement δ can be regarded as being proportional to the focusvalue.

    δ(f)=δ.sub.0 +δ.sub.1 •f           (5)

According to the second principle of the present invention, higherorders of the deflection distortion dependent on the height need not bemeasured, so that the time required for the adjustment of the entiresystem can be shortened. Also, failure to focus the beam at the time ofexposure is avoided, thereby to greatly reduce the blurring of patterns.

FIG. 9 is an illustrative drawing of a charged-particle-beam exposuredevice according to a first embodiment of the second principle.

A charged-particle-beam exposure device 30 of FIG. 9 includes thecharged-particle-beam generator 11, the deflector 12, the reflectiondetectors 13 and 14, the adder 15, the signal analyzing unit 16, aprojection lens 31, and a focus coil 32. The charged-particle-beamexposure device 30 also includes the XY stage 17 (not shown) and acontrol unit (not shown) in the same manner as in FIG. 5 to control thecharged-generator 11, the deflector 12, the signal analyzing unit 16,the XY stage 17, the projection lens 31, the focus coil 32, etc. In FIG.9, the same elements as those of FIG. 5 are referred by the samenumerals, and a description thereof will be omitted. A charged-particlebeam emitted from the charged-particle-beam generator 11 exposes apredetermined pattern on a wafer 33. On the wafer 33 are providedreference marks 34.

The focusing of the beam is carried out not by the projection lens 31provided at the bottom but by the focus coil 32. As shown in FIG. 9, thefocus coil 32 is provided separately from the beam-deflection field ofthe deflector 12. By changing the amount of an excitation currentapplied to the focus coil 32, it is possible to focus the beam on awafer surface without changing a deflected-beam path.

FIG. 10 is a flowchart of a process of obtaining thedeflection-efficiency-correction coefficients G(f) and R(f) as well asthe displacement δ(f).

At a step S21, a focus value (just focus) f_(i) and the correctioncoefficients G(f_(i)) and R(f_(i)) are measured by using three referencemarks M_(i) (i=1, 2, 3) provided at the height f_(i) (i=1, 2, 3),respectively. As the reference marks M_(i), marks 37 formed on a chip 36held in a slanted position in a wafer holder 35 can be used as shown inFIG. 11A. A method of achieving a just focus for obtaining the focusvalue f_(i) will be described later.

Dent marks may be used as the reference marks here. Also, thecontrast-detection-type marks with a buried heavy metal according to thefirst principle of the present invention may be used as the referencemarks. Alternately, contrast-detection-type marks as shown in FIGS. 11Band 11C may be used as the reference marks. In FIGS. 11B and 11C, acontrast-detection-type mark 21A is formed by patterning a heavy-metallayer 24A of such metal as Au, Ta, W, or the like on a the substrate23A. The heavy-metal layer 24A for forming the contrast-detection-typemark 21A has a thickness of about 0.2 μm.

At a step S22, G(f)=g₀ +g₁ •f is fitted by applying the least-squaremethod to G(f_(i)) (i=1, 2, 3) obtained above for the three points, sothat the coefficients g₀ and g₁ are obtained. R(f)=r₀ +r₁ •f is fittedby applying the least-square method to R(f_(i)) (i=1, 2, 3) obtainedabove for the three points, so that the coefficients r₀ and r₁ areobtained.

At a step S23, the reference mark M is moved to the center of thedeflection field.

At a step S24, the reference mark M is detected by using the just focusvalue f, a focus value f+df, and a focus value f-df (df is a change inthe focus value). By doing so, δ(f), δ(f+df), and δ(f-df) representingthe displacements of the entire deflection field depending on the focusvalue are measured.

At a step S25, δ(f)=δ₀ +δ₁ •f is fitted by applying the least-squaremethod to δ(f), δ(f+df), and δ(f-df) obtained above, so that thecoefficients δ₀ and δ₁ are obtained. This ends the procedure.

In this manner, the deflection-correction coefficients G(f) and R(f) aswell as the displacement δ(f) are easily and quickly obtained. Use ofthese values for exposure makes it possible to generate a preciseexposure pattern.

FIG. 12 is a flowchart of an exposure process for the wafer 33.

At a step S31, a plurality (m) of chips to be focused on are selectedbased on information about a chip arrangement on the wafer 33.

At a step S32, the beam is directed to a mark on the wafer 33 to measurethe focus value f₀. Here, this mark is a mark for the beam adjustmentlocated near the center of the beam optical system.

At a step S33, the beam is successively directed to the reference marks34 located at coordinates (X_(i), Y_(i)) in the m selected chips, sothat the focus values f(X_(i), Y_(i)) are obtained.

At a step S34, an interpolation function F(X, Y) is fitted to the focusvalues f(X_(i), Y_(i)) by applying the least-square method, wherein theinterpolation function F(X, Y) is provided as: ##EQU1## Through theleast-square fitting, the coefficients A_(k1) are obtained. Here, thehighest order n of the interpolation function is predetermined based ona flatness and a distortion of the wafer 33.

At a step S35, the positioning of the beam on the wafer 33 and anexposure thereof is carried out by using the focus distances obtainedfrom the interpolation function and the deflection-efficiency-correctioncoefficients obtained from the focus distances. Namely, the focus valueF(X, Y) is obtained by using a coordinate (X, Y) to be exposed on thewafer 33. Then, the focus value f of the focus coil 32 is set to F(X,Y), and the deflection-efficiency-correction coefficients G(f) and R(f)of the deflector 12 are set in accordance with the equation (3) and (4),respectively. Further, the displacement obtained by the equation (5) isincorporated in the deflection data of the deflector 12 to cancel thedisplacement.

FIGS. 13A and 13B are illustrative drawings for explaining a method ofdetecting the just focus (i.e., precision focus) value of thecharged-particle beam.

The charged-particle beam is scanned over a dent mark 43 in a chip 42covered with a resist 41, and reflected charged particles are detected.An exemplary detected reflection signal is shown in FIG. 13B. In orderto obtain the just focus value, the reflection signal of FIG. 13B issuccessively measured as the focusing of the beam is varied. Then, areflection signal having the steepest slope at an edge indicated by anarrow in FIG. 13B is selected from the reflection signals of variousfocus values. The focus value of this selected reflection signal is thejust focus value. The same method can be used for obtaining a just focusvalue for a contrast-detection-type mark.

FIG. 14 is an illustrative drawing of a charged-particle-beam exposuredevice according to a second embodiment of the second principle. In FIG.14, the same elements as those of FIG. 9 are referred by the samenumerals, and a description thereof will be omitted. Acharged-particle-beam exposure device 50 of FIG. 14 includes the XYstage 17 (not shown) and a control unit (not shown) in the same manneras in FIG. 5 to control the charged-particle-beam generator 11, thedeflector 12, the signal analyzing unit 16, the XY stage 17, theprojection lens 31, the focus coil 32, etc.

In FIG. 14, the charged-particle-beam exposure device 50 also includes alight sensor 51 and a height detector 52. The light sensor 51illuminates light on the wafer 33, and detects light reflectedtherefrom. Here, light which does not have a photosensitive effect onthe wafer 33 is used. An output from the light sensor 51 is provided tothe height detector 52. The height detector 52 measures the height of asurface of the wafer 33 based on the output from the light sensor 51. Inthis manner, when the reference marks 34 have such a structure that theheight thereof cannot be detected by the beam scan, the height of themark on the wafer is optically measured by using the height detector 52.

Here, the height f_(o) optically measured is different from the focusvalue (focus distance) f which is used for the charged-particle beam. Inorder to convert the height f_(o) to the focus value f, a differencef_(od) between the height and the focus value should be obtained. Byusing a reference mark to which both the optical measurement method andthe beam measurement method can be applied, the difference f_(od) isobtained as f_(o) -f. This process may be carried out only once inadvance. In order to perform the focusing and calibration of the beam,the focus value f can be calculated as f_(o) -f_(od).

According to the first and second embodiments of the second principle ofthe present invention, the focus value F(X, Y) at any point (X, Y) onthe wafer can be obtained in a short period of time. Based on theobtained focus value, the deflection-efficiency-correction coefficientsand the displacement, which are dependent on the focus value, are easilyobtained. Even in the case that the focusing of the beam fails for acertain reference mark or that the obtained focus values contain errorsto some extent, precise focusing of the beam is still possible becausethe interpolation function serves to smooth out a distribution of focusvalues. Also, there is a case in which the reference marks have such astructure that the focusing of the beam is difficult for these marks. Inthis case, the height of the mark is measured by the optical measurementmethod, so that the focus value of the focus coil can be determined.

Furthermore, instead of measuring the focus values at the same time asexposure or measuring the focus values for each chip, a global alignmentmethod used in positioning by an optical stepper may be used for thefocusing of the beam. In this case, a variation of the measurements or adeviation of the focus point can be eliminated.

In the following, a third principle of the present invention will bedescribed. The third principle is concerned with a device and a methodof exposing the charged-particle beam which can use correctioncoefficients provided for small units of areas without sacrificing theexposure processing time.

In the third principle of the present invention, data for obtaining thecorrection coefficients is collected and stored in a memory area priorto an exposure process. Then, the correction coefficients used for afirst frame are calculated from the data and stored prior to an exposureof the first frame. After that, the correction coefficients used for aN+1-th frame are calculated from the data and stored during an exposureof a N-th frame.

Memory means for storing the two-frame correction coefficients is aconventional memory having enough storage capacity. This memory meansmay have a memory area storing all the correction coefficients for twoframes such that the correction coefficients for one frame can bewritten while the correction coefficients for the other frame is read.In this case, writing/reading of the correction coefficients aresmoothly conducted. Such memory means includes a buffer memory, a FIFOmemory, a dual-port memory of a certain type, and a combination ofthese.

In the third principle of the present invention, when densely providedcomplex correction coefficients are set in the device for enhancement ofexposure precision, the calculation and storage of the correctioncoefficients are carried out in parallel with other processes requiredfor the exposure. Therefore, a large amount of calculation is carriedout, and the correction coefficients are set, without increasing theprocessing time for the exposure. That is, high-speed processing thesame as the prior-art device can be achieved. Furthermore, a largevolume memory is not necessary for the memory means. Since thecorrection coefficients for only two frames are stored in the memorymeans, updating of cell-correction coefficients and the like can beeasily and quickly carried out during the exposure.

Moreover, the data for the deflector correction may be newly collectedduring an exposure of the wafer, and the correction coefficients arecalculated by using the newly collected data and stored in the memorymeans. Thus, all the correction coefficients stored in the memory areado not have to be updated even when new correction data becomesnecessary during the exposure. Thus, a precise exposure pattern iscreated by using densely distributed correction coefficients withoutincreasing the exposure processing time.

FIG. 15 is a block diagram of an exemplary charged-particle-beamexposure device for conducting an exposure process according to thethird principle of the present invention.

In FIG. 15, a charged-particle-beam exposure device 100 includes anexposure-column unit 110 and a control unit 150. The exposure-columnunit 110 includes a charged-particle-beam generator 114 having a cathode111, a grid 112, and an anode 113. The exposure-column unit 110 furtherincludes a first slit 115 providing a rectangular shape of the chargedparticle beam, a first lens 116 converging the shaped beam, and a slitdeflector 117 deflecting a position of the shaped beam on a mask 120based on a deflection signal S1. The exposure-column unit 110 furtherincludes second and third lenses 118 and 119 opposing each other, themask 120 mounted movably in a horizontal direction between the secondand third lenses 118 and 119, and first-to-fourth deflectors 121 through124 deflecting the beam between the second and third lenses 118 and 119based on position information P1 through P4 to select one of a pluralityof holes provided through the mask 120. The exposure-column unit 110further includes a blanking 125 cutting off or passing the beamaccording to a blanking signal, a fourth lens 126 converging the beam,an aperture 127, a refocus coil 128, and a fifth lens 129. Theexposure-column unit 110 further includes a dynamic focus coil 130, adynamic stigmator coil 131, an objective lens 132 projecting the beam onto a wafer, and a main deflector 133 and a sub-deflector 134 positioningthe beam on the wafer according to exposure-position signals S2 and S3.The exposure-column unit 110 further includes a stage 135 carrying thewafer to move it in X-Y directions, and first-to-fourth alignment coils.

The control unit 150 includes a memory media 151 comprising a disk or MTrecorder for storing design data of integrated circuits, and a CPU 152controlling the charged-particle-beam exposure device. The control unit150 further includes a data-management unit 153, an exposure-managementunit 159, a mask-stage controlling unit 160, a main-deflector-deflectionsetting unit 161, and a stage controlling unit 162, all of which areconnected via a data bus (i.e., VME bus). Exposure data includesmain-deflector data and sub-deflector data, and is stored in a buffermemory 154 via the data-management unit 153 prior to the exposureprocess. The buffer memory 154 is used as a high-speed buffer forreading the exposure data, thereby negating an influence of low-speeddata reading from the memory media 151.

The main-deflector data is set in the main-deflector-deflection settingunit 161 via the exposure-management unit 159. The exposure-positionsignal S2 is output after the deflection amount is calculated, and isprovided to the main deflector 133 via the DAC/AMP 170. Then, thesub-deflection data for exposing a selected field is read from thedata-management unit 153, and is sent to the sub-deflector-deflectionsetting unit 155. In the sub-deflector-deflection setting unit 155, thesub-deflection data is broken down into shot data by the patterngenerating unit 156, and is corrected by the pattern-correction unit157. These circuits operates in a pipeline according to a clock signalgenerated by the clock setting unit 158.

After the processing of the pattern-correction unit 157, a signal S1 forsetting a slit size, mask-deflection signals P1 through P4 fordetermining a deflected position on the mask 120 of the beam deflectedaccording to the signal S1 after passing through the first slit 115, asignal S3 for determining a position on the wafer of the beam shaped bythe mask 120, and a signal S4 for correcting distortion and blurring ofthe beam are obtained. Also, the clock setting unit 158 provides ablanking controlling unit 165 with a B signal for controlling theblanking operation.

An exposure position on the wafer is controlled by the stage controllingunit 162. In doing so, a coordinate position detected by a laserinterferometer 163 is supplied to the stage controlling unit 162.Referencing to the coordinate position, the stage controlling unit 162moves the stage 135 by driving a motor 164.

In this manner, the control unit 150 controls the exposure-column unit110 such that the charged-particle beam emitted from thecharged-particle-beam generator 114 is rectangularly shaped by the firstslit 115, converged by the lenses 116 and 118, deflected by the maskdeflectors 121 and 122, and directed to the mask 120. The beam havingpassed through the mask 120 passes through the blanking 125, isconverged by the fourth lens 126, is deflected to a center of asub-field of about 100-μm square by the main deflector 133, and isdeflected within this sub-field by the sub-deflector 134.

Elements concerning the detection and analysis of reflection signalsnecessary for the positioning of the wafer and the calibration of thebeam are the same as those shown in FIG. 5, and, thus, are omitted inFIG. 15.

FIG. 16 is a block diagram of a correction-coefficient calculating andsetting unit according to a first embodiment of the third principle. Thecorrection-coefficient calculating and setting unit is used in thecharged-particle-beam exposure device 100 of FIG. 15.

In FIG. 16, a correction-coefficient calculating and setting unit 200includes a positioning-information measuring unit 201, aheight-variation-information measuring unit 202, a data-memory unit 203,a first coefficient calculating unit 204, a second coefficientcalculating unit 205, a first coefficient storing unit 206, a secondcoefficient storing unit 207, a first correction calculating unit 208,and a second correction calculating unit 209.

The positioning-information measuring unit 201 obtains data forpositioning the wafer to be exposed. This data includes a displacementof a beam deflected to a mark as well as beam-size-reductioninformation. The height-variation-information measuring unit 202 obtainsdata regarding a variation in the height of the wafer. The data measuredby the positioning-information measuring unit 201 and theheight-variation-information measuring unit 202 is stored in thedata-memory unit 203. The measurement and storing of the data arefinished by the start of an exposure. The positioning-informationmeasuring unit 201 and the height-variation-information measuring unit202 are implemented by the reflection detectors 13 and 14, the adder 15,and the signal analyzing unit 16 of FIG. 5, for example. The data-memoryunit 203 is implemented by the memory media 151 and the buffer memory154 of FIG. 15.

Immediately before the start of an exposure, the beam is adjusted. Then,the wafer is moved through stage movement to a position where a firstframe is started to be drawn, i.e., the wafer is moved from a positionwhere the beam is adjusted to a position where the exposure is started.This stage movement is controlled by the stage controlling unit 162.

The first coefficient calculating unit 204 and the second coefficientcalculating unit 205 receive information on a frame position from theCPU 152 controlling the stage controlling unit 162. Based on thisinformation, the first coefficient calculating unit 204 and the secondcoefficient calculating unit 205 calculate the correction coefficientsused for a given cell field at the time of a first-frame exposure, andstore these correction coefficients in the first coefficient storingunit 206 and the second coefficient storing unit 207, respectively. Thebeam adjustment and the stage movement before the start of an exposuretake at least 2 seconds. The calculation of the correction coefficientspreviously described is easily conducted within this time interval.

The first coefficient calculating unit 204, the first coefficientstoring unit 206, and the first correction calculating unit 208 areimplemented by the main-deflector-deflection setting unit 161 of FIG.15. The second coefficient calculating unit 205, the second coefficientstoring unit 207, and the second correction calculating unit 209 areimplemented by a sub-deflector-deflection setting unit 155 of FIG. 15.

After the exposure of the first frame is started, the first coefficientcalculating unit 204 and the second coefficient calculating unit 205calculate the correction coefficients for the second frame, and storethe correction coefficients in the first coefficient storing unit 206and the second coefficient storing unit 207, respectively. In the samemanner, while an N-th frame is being exposed, the correctioncoefficients used for an N+1-th frame are calculated. Even if thecalculation and storing of the correction coefficients for the N+1-thframe are completed before the end of the exposure of the N-th frame,the correction coefficients used for the next (N+2-th) frame are notcalculated.

An address corresponding to each cell field of two frames is necessaryin the first coefficient storing unit 206 and the second coefficientstoring unit 207. When a wafer of an 8-inch diameter is used with a cellfield of a 1-mm square, the number of addresses required for one frameis 200. 400 addresses are used for two frames. Thus, only a small memoryvolume is required. Here, each correction coefficient needs 32 bits.

The correction coefficients needing to be updated during an exposureinclude area-correction coefficients (G, R, D, and δ) for correcting abeam within an area totaling 8 coefficients for X and Y coordinates, 8cell-correction coefficients for transforming coordinates of the maindeflector with respect to the stage-movement directions, 8stage-correction coefficients for aligning the stage-movement directionswith wafer coordinates at the time of continuous stage movement, andcorrection coefficients for determining the beam focus value for eachcell. The area-correction coefficients may be updated at the time whenthe beam shifts across an area border during the stage movement. Othercorrection coefficients need to be updated for each cell. Hereinafter,correction coefficients needing to be updated for each cell arecollectively called cell-correction coefficients.

The first correction calculating unit 208 and the second correctioncalculating unit 209 read the correction coefficients from the firstcoefficient storing unit 206 and the second coefficient storing unit207, respectively. These correction coefficients are supplied to themain deflector and the sub-deflector.

FIG. 17 is a block diagram of a coefficient storing unit according to asecond embodiment of the third principle. In the second embodiment, thefirst coefficient storing unit 206 and the second coefficient storingunit 207 of the first embodiments are controlled such that thecorrection coefficients for one frame can be written while thecorrection coefficients for another frame are being read.

The first coefficient storing unit 206 and the second coefficientstoring unit 207 of FIG. 16 store all the correction coefficients setfor the cell fields of two frames. In order to smoothly carry out thereading and writing of the correction data, it is necessary to write thecorrection coefficients for one frame while the correction coefficientsfor another frame are being read.

The first coefficient storing unit 206 or the second coefficient storingunit 207 of FIG. 17 includes an inverter 210 and frame-coefficientstoring units 211 and 212. A mode selection signal takes a value of 0 or1, and determines which one of a writing mode and a reading mode isused. The frame-coefficient storing unit 211 receives the mode selectionsignal, and the frame-coefficient storing unit 212 receives an invertedmode selection signal output from the inverter 210. When the modeselection signal indicates the writing mode, therefore, the correctioncoefficients are written into the frame-coefficient storing unit 211,and are read out from the frame-coefficient storing unit 212. On theother hand, when the mode selection signal indicates the reading mode,therefore, the correction coefficients are read from theframe-coefficient storing unit 211, and are written in theframe-coefficient storing unit 212.

The mode selection signal reverses each time when an exposure processmoves from one frame to a next frame. Hereinafter, the mode selectionsignal is called a frame-control flag. The frame-control flag may beprovided from the CPU 152 of FIG. 15. In this manner, thewriting/reading of data is controlled such that the correctioncoefficients for one frame can be written while the correctioncoefficients for another frame are being read.

The frame-coefficient storing units 211 and 212 of FIG. 17 may include abuffer memory, a FIFO memory, a dual-port memory of a certain type, or acombination of these. When it includes a buffer memory, control ofwriting addresses and reading addresses is necessary. When a FIFO memoryis used, control of addresses is not necessary as in a buffer memorysince the correction coefficients are read in an order in which they arewritten. However, the control coefficients cannot be used repeatedly inthe FIFO memory.

FIG. 18 is a block diagram showing an example in which a dual-portmemory is used as the frame-coefficient storing unit 211 and theframe-coefficient storing unit 212 of FIG. 17.

When a dual-port memory 220 is used as shown in FIG. 18, an MSB (mostsignificant bit) of the memory is used as the frame-control flag. Theframe-control flag is reversed by an inverter 223 on a data reading sideas compared to a data writing side. At a time when a frame is changed(i.e., when the stage movement takes a U-turn), the frame-control flagis reversed. Addresses other than the MSB are used as addresses forstoring the correction coefficients by the coefficient calculating unit221 (204 or 205). In the same manner, the correction calculating unit222 (208 or 209) uses the addresses other than the MSB as addresses forreading the correction coefficients. Thus, when the correctioncoefficients are written in either one of the upper or lower half of thememory space, the correction coefficients are read from the other half.

By using the dual-port memory 220 as shown in FIG. 18, the calculationand setting of the correction coefficients are conducted withoutrequiring complex control of an updating timing and a reading timing ofthe correction coefficients. Also, there is an advantage in thataddresses of the correction coefficients for wafer coordinates can bematched between when the data is written and when the data is read.

FIG. 19 is an illustrative drawing showing portions in one area whereframe exposures begin and end. In FIG. 19, cells are denoted by l-1,l-2, m-1, m-2, n-1, and n-2. The cell-correction coefficients for eachcell are different for a different cell, and the area-correctioncoefficients for one area are the same for all the cells in FIG. 19.While an m-th frame is under an exposure, the correction coefficientsfor an n-th frame are calculated and stored in the coefficient storingunit. However, the area-correction coefficients for the m-th frame andthe n-th frame are the same so that there is no need to update thearea-correction coefficients in this case.

FIG. 20 is a block diagram of a portion for controlling the updating ofthe cell-correction coefficients and the area-correction coefficientsaccording to a third embodiment of the third principle of the presentinvention.

According to the third embodiment of the third principle, the updatingof the cell-correction coefficients and the area-correction coefficientsare controlled by an exposure controlling unit. The exposure controllingunit may be implemented in the exposure-management unit 159 of FIG. 15.

In FIG. 20, an exposure controlling unit 230 provides a correctioncalculating unit 231 with a timing signal indicating a timing of acell-to-cell shift and a timing of an area-to-area shift. The correctioncalculating unit 231 reads the correction coefficients from acoefficient storing unit 232 based on the timing signal. Namely, thecorrection calculating unit 231 reads the cell-correction coefficientsfrom the coefficient storing unit 232 at a timing of a cell-to-cellshift, and reads the area-correction coefficients as well as thecell-correction coefficients at a timing of an area-to-area shift.

In order to provide the timing signal indicating a timing of acell-to-cell shift and a timing of an area-to-area shift, the exposurecontrolling unit 230 needs to keep a constant observation of exposurepositions. This is achieved by using a counter or the like for countinga cell number and an area number.

FIG. 21 is a block diagram of a variation of the third embodiment of thethird principle. In this variation, a pattern of stored correctioncoefficients is kept in a memory. Information on thecorrection-coefficient pattern is provided to the correction calculatingunit 231 based on the timing signal.

In FIG. 21, an exposure controlling unit 230A provides a timing signalto a correction calculating unit 231A and to acorrection-coefficient-pattern storing unit 233. Thecorrection-coefficient-pattern storing unit 233 keeps a pattern of thestored correction coefficients, and provides the correction calculatingunit 231A with information indicating an area-to-area shift or acell-to-cell shift. In this configuration, the updating of thecorrection coefficients can be controlled based only on an output of thecorrection-coefficient-pattern storing unit 233.

An example of the correction-coefficient pattern is shown in FIG. 22. InFIG. 22, "00" of first data (00, AREA) indicates that a cell to beexposed next is a first cell, and "AREA" thereof indicates that thiscell belongs to a new area. "01" of second data (01, CELL) indicate thata cell to be exposed next is a second cell, and "CELL" thereof indicatesthat there is no area change. In the example of FIG. 22, fifth data (04,AREA) indicates that a fifth cell belongs to a new area. Namely, thefirst area includes four cells in FIG. 22. The correction-coefficientpattern of FIG. 22 is merely an example, and variations thereof may beused in the present invention to indicate needs, as well as no need, forupdating particular ones of the correction coefficients.

The correction-coefficient-pattern storing unit 233 of FIG. 21 maypreferably include a buffer memory, a FIFO memory, or a dual-portmemory. Among these memories, the FIFO memory is the best. Thecorrection-coefficient pattern is determined based on exposurearrangement information, so that an entire correction coefficientpattern covering up to an end of an exposure can be determined at a timeof a beginning of the exposure. Thus, it is preferable to use a FIFOmemory in terms of convenience of use since the FIFO memory has such astructure that data can be consecutively read and written.

FIG. 23A is a circuit diagram of an example of a dual-port memorycontrolled by the configuration of FIG. 17. In FIG. 23A, theframe-control flag is assigned to the MSB of address lines of thedual-port memory, and left-hand-side data of the FIFO output of FIG. 22,i.e., "00, 01, 02, . . . ", is input to bits other than the MSB. Here, aDSP (digital signal processor) is used as the correction calculatingunit 231A.

A circuit of FIG. 23A includes the correction calculating unit 231A,dual-port memories 251 and 252, an inverter 253, a decoder 254, acorrection-coefficient-updating-pattern register 255, a resister 256,and inverters 257 and 258. The dual-port memories 251 and 252 receiveVMED (address and data), VMEA (address), a write strobe signal WRITESTB, and a read strobe signal READ STB from the coefficient calculatingunit.

The least significant bit of an address signal is provided to achip-selection node CS of the dual-port memory 251. Also, a reversedsignal of the least significant bit by the inverter 253 is input to achip-selection node CS of the dual-port memory 252. Thus, data providedto the circuit is supplied in turn to one of the dual-port memory 251and the dual-port memory 252. The reason why the dual-port memory 251and the dual-port memory 252 are provided is because the two dual-portmemory, rather than one, can increase a memory volume to store morecorrection coefficients. In FIG. 23A, bits 4 through 11 of addressinputs on a data writing side are provided with data on the data businstead of address data on the address bus. This is because thisconfiguration can boost a processing speed. In this configuration, thedata on the data bus is decoded by the decoder 254 to determine anaddress.

FIG. 23B is a chart showing data to be stored in the dual-port memory251, for example. As shown in FIG. 23B, the lowest four bits (bits 0through 3) of the address correspond to each correction coefficient, andeight bits (bits 4 through 11) next to these four bits represent a cellnumber. Thus, assuming that a correction coefficient R_(ac) is stored atan address of a hexagonal 3 of the lowest four bits, R_(ac) for a firstcell is stored at an address "003", and R_(ac) for a 256-th cell isstored at an address "FF3".

Assume that data is output from the FIFO as shown in FIG. 22. An upperaddress of the dual-port memory 251 or the dual-port memory 252 isdetermined by the first data (00, AREA). For example, the dual-portmemory 251 may be selected by the correction calculating unit 231A as achip to be used. In this case, based on information "AREA" of the firstdata, the correction calculating unit 231A reads all the data stored inaddresses 0 through 9 of the dual-port memory 251 to use the data forcorrection of the charged-particle beam. After an exposure of a firstcell is completed, the second data (01, CELL) is provided from the FIFOto determine the upper address of the dual-port memory 251. Based oninformation "CELL" of the second data, the correction calculating unit231A reads data stored in addresses 0 through 5 to use the data forcorrection of the beam.

The correction-coefficient-updating-pattern register 255 is arranged inparallel with the dual-port memories 251 and 252. Thecorrection-coefficient-updating-pattern register 255 is used when thecorrection coefficients are controlled at a level finer than the levelof the area-correction coefficients and the cell-correction coefficientssuch that some of the area correction coefficients are not updated at acertain timing, etc. By using information stored in thecorrection-coefficient-updating-pattern register 255, the correctioncalculating unit 231A can avoid reading unnecessary correctioncoefficients based on information about the correction coefficientsneeded to be updated. There is a case in which all the correctioncoefficients do not have to be updated when an exposure is made. In acase where requirements for an exposed-pattern precision are not sohigh, for example, a desired precision may be achieved withoutfrequently changing the correction coefficient. In this case,information on the correction coefficients with no need to be updated isstored in the correction-coefficient-updating-pattern register 255 inadvance. Then, before the start of an exposure, this information isinput to input ports of the correction calculating unit (DSP) 231A.Based on this information, the correction calculating unit (DSP) 231Areads only necessary correction coefficients from the dual-port memories251 and 252 to update them during the exposure.

In the third principle, when the complex and densely distributedcorrection coefficients are set for an enhancement of exposureprecision, the calculation and setting of the correction coefficientsare carried out in parallel with other processes required for theexposure. Thus, the calculation and setting of a large number ofcorrection coefficients are conducted without increasing the processingtime for the exposure. Also, there is no need for a large memory volume,only the correction coefficients for two frames being stored. Therefore,the cell-correction coefficients can be easily updated at high speedduring the exposure. As a result, it is possible to create an exposurepattern only by taking almost the same processing time as required inthe related art without sacrificing the precision. Thus, the thirdprinciple of the present invention greatly contributes to thedevelopment of the manufacturing technology for the LSI chips havingfine patterns.

As described above, according to the present invention, the measureddeflection-efficiency-correction coefficients are approximated by usingthe linear functions of the focus distance, thedeflection-efficiency-correction coefficients are easily obtained asfunctions of the focus distance.

Also, according to the present invention, the measured displacement isapproximated to by using the linear function of the focus distance, thedisplacement is easily obtained as a function of the focus distance.

Also, according to the present invention, the height of the wafersurface is approximated as a function of the coordinates to provide thefocus distances, and the positioning and exposure of the wafer areconducted by using the deflection-correction coefficients and thedisplacement corrected with respect to the focus distances. Therefore,the data collection for correction of the beam does not require muchtime and labor, yet a precise exposure pattern being created.

Also, according to the present invention, the height of the wafersurface is optically measured even when focusing on the reference marksfails. Therefore, a precise exposure pattern is created for wafershaving any types of reference marks.

Furthermore, according to the present invention, the position-detectionmarks of the contrast-detection type allowing a detection based ondifferences in the reflection intensities are used. Thus, errors in thedetection of mark positions are eliminated.

Also, according to the present invention, the position-detection marksof the contrast-detection type having a high precision of surfaceflatness are used. Thus, errors in the detection of mark positions areeliminated.

Also, according to the present invention, the position-detection marksof the contrast-detection type allowing a detection based on differencesin the reflection intensities are used. Thus, the deflection-distortionmap and the deflection-efficiency-correction coefficients free fromerrors are obtained.

Also, according to the present invention, the position-detection marksof the contrast-detection type allowing a detection based on differencesin the reflection intensities are used to expose the wafer aftercorrecting the charged-particle beam. Therefore, a precise exposurepattern is created.

Also, according to the present invention, the distortion of thecharged-particle beam is corrected by using the position-detection marksof the contrast-detection type allowing a detection based on differencesin the reflection intensities, and the deflection efficiency of the beamis corrected by canceling the measurement errors in thecorrection-efficiency-correction coefficients obtained from thepositioning marks or the beam adjustment marks provided on the wafer.Therefore, a precise exposure pattern is created on the wafer.

Also, according to the present invention, the positioning marks may bedetected at the center axis of the beam optical system to eliminateerrors in the detection of the positioning marks.

Furthermore, according to the present invention, the correctioncoefficients for a N+1-th frame are calculated while the correctioncoefficients for a N-th frame are being exposed, so that the exposureprocess and the calculation of the correction coefficients are conductedin parallel (simultaneously). Thus, a precise exposure pattern iscreated by using densely distributed correction coefficients withoutincreasing the exposure processing time.

Also, according to the present invention, it is sufficient to store onlythe correction coefficients for two frames. Thus, a precise exposurepattern is created by using densely distributed correction coefficientswithout increasing the exposure processing time.

Also, according to the present invention, the writing and reading of thecorrection coefficients are smoothly conducted in parallel. Thus, aprecise exposure pattern is created by using densely distributedcorrection coefficients without increasing the exposure processing time.

Also, according to the present invention, the correction coefficientswith no need to be updated are not updated during an exposure of a givenframe to achieve an efficient correction of the deflector. Thus, aprecise exposure pattern is created by using densely distributedcorrection coefficients without increasing the exposure processing time.

Also, according to the present invention, the correction coefficientsfor a given frame are updated while another frame is being exposed.Thus, a precise exposure pattern is created by using densely distributedcorrection coefficients without increasing the exposure processing time.

Also, according to the present invention, the data for the deflectorcorrection may be newly collected during an exposure of the wafer, andthe correction coefficients are calculated by using the newly collecteddata. Thus, the correction coefficients stored in the memory do not haveto be updated even when new correction data become necessary during theexposure. Thus, a precise exposure pattern is created by using denselydistributed correction coefficients without increasing the exposureprocessing time.

Moreover, there are other problems concerning the present invention, andthese problems will be described below.

The charged-particle-beam exposure method has superior characteristicsin terms of the resolution and the focus depth, compared to the lightexposure method widely used in the manufacturing of LSI chips. However,the charged-particle-beam exposure method is inferior in terms of anexposure positioning accuracy and an overlay accuracy. Thus, thecharged-particle-beam exposure method is not widely used in the fieldfor manufacturing purposes.

In general, a charged-particle-beam exposure device controls acharged-particle beam through an electromagnetic field to draw patternson photosensitive material. Therefore, the positioning of the beam canbe corrected for each pattern. On the other hand, a correction operationis complex, and a beam adjustment (calibration) for determining variouscorrection coefficients is lengthy.

The charged-particle-beam exposure device generally has a main deflectorfor deflecting the beam within a large area and a sub-deflector fordeflecting the beam within a small area at high speed. A combination ofthese two deflectors makes it possible to draw patterns in a large areaat high speed. Typically, the main deflector is a coil, and thesub-deflector is a static-charge deflector.

The charged-particle beam deflected by the main deflector passes throughan electric field generated by the sub-deflector with the electric fielddeflecting the beam at high speed. In this case, a position of the beampassing through the sub-deflector varies according to the deflectionamount (deflection angle) incurred by the main deflector. Since there isa distortion in the electric field generated by the sub-deflector, avariation in the position of the passing beam leads to the deflectionamount of the sub-deflector being changed accordingly.

In the charged-particle-beam exposure device having more than onedeflector, therefore, a deflection efficiency of the sub-deflector ischanged depending on the path of the charged-particle beam deflected bythe main deflector. In order to correct a distribution of the deflectionefficiency, typically, the deflection efficiency of the sub-deflector ismeasured for each deflection amount of the main deflector.

FIG. 24 is an illustrative drawing showing a first related-art method ofobtaining a map of deflection-efficiency-correction coefficients of thesub-deflector. The first related-art method will be described withreference to FIG. 24.

In an example of FIG. 24, a deflection area of the main deflector is a2000-μm square, and a deflection area of the sub-deflector is a 100-μmsquare. The deflection area of the main deflector is divided into 400(20×20) fields of a 100-μm square. Within this field, a pattern is drawnby deflecting the beam through the sub-deflector without using the maindeflector. The area of the 2000-μm square is called a main field, andthe area of the 100-μm square is called a sub-field.

In this example, the sub-deflector's deflection efficiency should bemeasured at 20×20 points of deflection positions of the main deflector,each of the 20×20 points being arranged in a corresponding one of the100-μm squares. A procedure for measuring the sub-deflector's deflectionefficiency at the 20×20 points includes the steps of:

(1) setting the deflection position of the main deflector at a center ofa sub-field (Ix, Iy);

(2) carrying out the following two steps at the four corners of thesub-field;

(2)-1 positioning a position-detection mark at a corner of the sub-fieldthrough stage movement;

(2)-2 deflecting the beam through the sub-deflector to the cornerprovided with the position-detection mark to detect a position of theposition detection mark;

(3) calculating deflection-efficiency-correction coefficients based ondifferences between the detected positions of the mark and the actualpositions (as defined by the stage movement) thereof at the fourcorners; and

(4) repeating the steps (1) through (3) for all the sub-fields at Ix=1,2, . . . , 20 and Iy=1, 2, . . . , 20.

This procedure takes time for the measurement since 1600 (20×20×4) stagemovements are required. Assuming that a time period required for a stagevibration caused by the stage movement to be settled is 500 ms, themeasurement of all the correction coefficients for the sub-fields takes13 minutes and 20 seconds (800 seconds).

In response, a method of reducing the number of the stage movements toone fourth without decreasing the number of the measurement points hasbeen proposed. FIG. 25 is an illustrative drawing showing a secondrelated-art method of obtaining a map ofdeflection-efficiency-correction coefficients of the sub-deflector.

In an example of FIG. 25, sizes of the main field and the sub-field arethe same as in the first related-art method. A procedure for measuringthe sub-deflector's deflection efficiency at the 20×20 points includesthe steps of:

(1) positioning a position-detection mark at a center of a sub-field(Ix, Iy) through stage movement, and setting the deflection position ofthe main deflector at the center of the sub-field (Ix, Iy);

(2) carrying out the following three steps at the four corners of thesub-field;

(2)-2 deflecting the beam at a corner of the sub-field through thesub-deflector;

(2)-2 deflecting the beam back to the center of the sub-field throughthe main deflector;

(2)-3 detecting a position of the position-detection mark at the centerof the sub-field by using the beam;

(3) calculating deflection-efficiency-correction coefficients based ondifferences between the detected positions of the mark and the actualposition (as defined by the stage movement) thereof; and

(4) repeating the steps (1) through (3) for all the sub-fields at Ix=1,2, . . . , 20 and Iy=1, 2, . . . , 20.

This procedure does not require a stage movement at the step (2), sothat the number of the stage movements becomes equal to the number ofsub-fields, which is 400 (20×20) in this case. Assuming that a timeperiod required for a stage vibration caused by the stage movement to besettled is 500 ms, the measurement of all the correction coefficientsfor the sub-fields takes 3 minutes and 20 seconds (200 seconds). Thistime period is one-fourth of that of the first related-art method.

However, the second related-art method has a drawback in that errorsinvolved in the measured coefficients become large when thesub-deflector's deflection efficiency has much dependency on thedeflection amount of the main deflector. In order to measure thesub-deflector's deflection efficiency for the sub-field (Ix, Iy), thedeflection amount of the main deflector should be set at the center ofthis sub-field. In the second related-art method, however, thedeflection amount of the main deflector is changed at the step (2)-2.Strictly speaking, the second related-art method measures thedifferences between the detected positions and the actual positions ofthe mark at the corners of a sub-field displaced by (50 μm, 50 μm) fromthe actual sub-field. Assuming that the deflection efficiency of thesub-field displaced by (50 μm, 50 μm) is different from that of theactual sub-field by 0.1%, the differences at the corners contain errorsof 0.05 μm. Thus, correct deflection-efficiency-correction coefficientsare not obtained.

The first related-art method does not contain such errors. However, itrequires four times as long a measurement time as that of the secondrelated-art method as previously described.

Accordingly, there is a need in the field of a beam adjustment ofcharged-particle-beam exposure devices for a method which can carry outa more precise deflection-efficiency correction than the related-artmethods without sacrificing the processing time.

In the following, fourth and fifth principles of the present inventionand embodiments thereof will be described with reference to theaccompanying drawings.

FIG. 26 is an illustrative drawing showing the fourth principle of thepresent invention. In the fourth principle, four position-detectionmarks arranged at relative positions corresponding to the four cornersof a sub-field are used as shown in FIG. 26. First, a stage is moved soas to position the position-detection marks at the four corners of agiven sub-field. Then, the main deflector deflects the charged-particlebeam to a center of the given sub-field. Further, the sub-deflectorsuccessively deflects the charged-particle beam to the corners of thegiven sub-field to detect positions of the position-detection marks.

In this manner, data for the four corners of the given sub-field isobtained through only one stage movement. In this case, thecharged-particle beam deflected by the main deflector is positioned atthe center of the given sub-field, thereby generating no error in thedeflection-efficiency-correction coefficients. However, if the fourposition-detection marks contain errors in their relative positions,these errors will be contained in the sub-deflector'sdeflection-efficiency-correction coefficients for all the sub-fields.Namely, all the sub-fields will have the same errors. In order toeliminate these errors, one of the following methods may be used:

(1) correcting the correction coefficients at a time of the datameasurement by using arrangement errors of the position-detection marksmeasured in advance and stored in a memory;

(2) correcting the correction coefficients by using the arrangementerrors of the position-detection marks measured through stage movementat the time of the data measurement; and

(3) positioning one of the position-detection marks through stagemovement at a center of a sub-field located at a center of the mainfield after the data measurement, deflecting the beam at the center ofthe sub-field using the main deflector, deflecting the beam successivelyat the four corners of the sub-field using the sub-deflector, detectingthe one of the position-detection marks after directing the beam back tothe center of the sub-field using the main deflector, and correctingerrors of the sub-deflector based on an assumption that the maindeflector contain no error in the deflection thereof.

In either one of these three methods, the same error compensation can beapplied to all the sub-fields.

According to the fourth principle of the present invention, thecharged-particle beam deflected by the main deflector is positioned atthe center of the main deflector, so that there is no error in thecorrection coefficients. Also, the number of stage movements is onefourth that of the first related-art method, and is the same as that ofthe second related-art method, so that the data measurement time israther short. In the case in which the number of sub-fields is 20×20 andthe time length for the stage vibration to subside is 500 ms, thecorrection data is measured taking 3 minutes and 20 seconds (20×20×0.5sec).

The above description of the fourth principle has been given by takingan example of four position-detection marks. However, it is apparentthat the time length required for the data measurement is shorter thanthat of the first related-art method as long as more than oneposition-detection mark is used.

FIG. 27 is an illustrative drawing showing the fifth principle of thepresent invention. In the fifth principle, one position-detection markis positioned through stage movement at a point where four surroundingsub-fields share a corner point thereof, as shown in FIG. 27. Then, themain deflector deflects the charged-particle beam to a center of one ofthe four surrounding sub-fields. Further, the sub-deflector deflects thecharged-particle beam to the position-detection mark to detect aposition of the position-detection mark and to store a differencebetween the detected position and the actual position of the mark. Thesame procedure is carried out for the four surrounding sub-fields.

In this manner, the correction data is measured for a respective cornerof the four surrounding sub-fields, requiring only one stage movement.This data measurement is carried out at all the sub-field corners. Then,the correction coefficients are calculated based on the detecteddifferences for each of the sub-fields.

According to the fifth principle of the present invention, thecharged-particle beam deflected by the main deflector is positioned atthe center of the main deflector, so that there is no error in thecorrection coefficients. Also, the number of stage movements is onefourth that of the first related-art method, and is almost the same asthat of the second related-art method, so that the data measurement timeis rather short. In the case in which the number of the sub-fields is20×20 and the time length for the stage vibration to subside is 500 ms,the correction data is measured taking 3 minutes and 20 seconds(20×20×0.5 sec).

In the following, embodiments of the fourth and fifth principles of thepresent invention will be described with reference to the accompanyingdrawings.

FIG. 28 is a block diagram of an exemplary charged-particle-beamexposure device carrying out a deflection-efficiency correctionaccording to the fourth and fifth principles of the present invention.

In FIG. 28, a charged-particle-beam exposure device 400 includes anexposure-column unit 410 and a control unit 450. The exposure-columnunit 110 includes a charged-particle-beam generator 414 having a cathode411, a grid 412, and an anode 413. The exposure-column unit 410 furtherincludes a first slit 415 providing a rectangular shaping of the chargedparticle beam, a first lens 416 converging the shaped beam, and a slitdeflector 417 deflecting a position of the shaped beam on a mask 420based on a deflection signal S1. The exposure-column unit 410 furtherincludes second and third lenses 418 and 419 opposing each other, themask 420 mounted movably in a horizontal direction between the secondand third lenses 418 and 419, and first-to-fourth deflectors 421 through424 deflecting the beam between the second and third lenses 418 and 419based on position information P1 through P4 to select one of a pluralityof holes provided through the mask 420. The exposure-column unit 410further includes a blanking 425 cutting off or passing the beamaccording to a blanking signal, a fourth lens 426 converging the beam,an aperture 427, a refocus coil 428, and a fifth lens 429. Theexposure-column unit 410 further includes a dynamic focus coil 430, adynamic stigmator coil 431, an objective lens 432 projecting the beamonto a wafer, and a main deflector 433 and a sub-deflector 434positioning the beam on the wafer according to exposure-position signalsS2 and S3. The exposure-column unit 410 further includes a stage 435carrying the wafer to move it in X-Y directions, and first-to-fourthalignment coils.

The control unit 450 includes a memory media 451 comprising a disk or MTrecorder for storing design data of integrated circuits, and a CPU 452controlling the charged-particle-beam exposure device. The control unit450 further includes a data-management unit 453, an exposure-managementunit 459, a mask-stage controlling unit 460, a main-deflector-deflectionsetting unit 461, and a stage controlling unit 462, all of which areconnected via a data bus (i.e., VME bus). Exposure data includesmain-deflector data and sub-deflector data, and is stored in a buffermemory 454 via the data-management unit 453 prior to the exposureprocess. The buffer memory 454 is used as a high-speed buffer forreading the exposure data, thereby negating an influence of low-speeddata reading from the memory media 451.

The main-deflector data is set in the main-deflector-deflection settingunit 461 via the exposure-management unit 459. The exposure-positionsignal S2 is output after the deflection amount is calculated, and isprovided to the main deflector 433 via the DAC/AMP 470. Then, thesub-deflection data for exposing a selected field is read from thedata-management unit 453, is broken down into shot data by the patterngenerating unit 456, and is corrected by the pattern-correction unit457. These circuits operates in a pipeline according to a clock signalgenerated by the clock setting unit 458.

After the processing of the pattern-correction unit 457, a signal S1 forsetting a slit size, mask-deflection signals P1 through P4 fordetermining a deflected position on the mask 420 of the beam deflectedaccording to the signal S1 after passing through the first slit 415, asignal S3 for determining a position on the wafer of the beam shaped bythe mask 420, and a signal S4 for correcting distortion and blurring ofthe beam are obtained. Also, the clock setting unit 458 provides ablanking controlling unit 465 with a B signal for controlling theblanking operation.

An exposure position on the wafer is controlled by the stage controllingunit 462. In doing so, a coordinate position detected by a laserinterferometer 463 is supplied to the stage controlling unit 462.Referencing to the coordinate position, the stage controlling unit 462moves the stage 435 by driving a motor 464.

In this manner, the control unit 450 controls the exposure-column unit410 such that the charged-particle beam emitted from thecharged-particle-beam generator 414 is rectangularly shaped by the firstslit 415, converged by the lenses 416 and 418, deflected by the maskdeflectors 421 and 422, and directed to the mask 420. The beam havingpassed through the mask 420 passes through the blanking 425, isconverged by the fourth lens 426, is deflected to a center of asub-field of an about 100-μm square by the main deflector 433, and isdeflected within this sub-field by the sub-deflector 434.

FIG. 29 is an illustrative drawing showing a mark-position detectingportion of the charged-particle-beam exposure device 400. In FIG. 29,the mark-position detecting portion includes reflection detectors 480and 481, a signal analyzing device 482, and a control-purpose computer483. The control-purpose computer 483 includes the CPU 452 of FIG. 28,RAM, and ROM.

As shown in FIG. 29, a position-detection mark 485 may be formed from aheavy-metal layer patterned on a silicon 484. The charged-particle-beamexposure device 400 scans the charged-particle beam over the silicon 484and the position-detection mark 485 in predetermined directions. Thereflection detectors 480 and 481 detect charged particles scattered bythe silicon 484 or the position-detection mark 485. The signal analyzingdevice 482 analyzes a reflection signal obtained by scanning thecharged-particle beam, and detects a position of the position-detectionmark 485 based on a difference in reflection intensities between theposition-detection mark 485 and the silicon 484.

FIG. 30 is an illustrative drawing showing a reference chip 490 providedwith four position-detection marks according to the fourth principle ofthe present invention. The reference chip 490 is placed on the stage 435of the charged-particle-beam exposure device 400. The reference chip 490is preferably a heavy-metal layer such as Ta, W, Au, or the likepatterned on an Si wafer.

FIG. 31 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector according to a first embodiment of thefourth principle.

At a step S41, the reference chip 490 is placed on the stage 435 of thecharged-particle-beam exposure device 400.

At a step S42, positions of the four position-detection marks aredetected at a center of the main field, and errors of the relativepositions of the four position-detection marks are stored in a memory ofthe control-purpose computer 483.

At a step S43, position errors (differences between detected positionsand actual positions of the four position-detection marks) are measured.First, a center of the four position-detection marks is moved to acenter of a given sub-field, and the charged-particle beam is deflectedthrough the main deflector to the center of the sub-field. Then, thecharged-particle beam is successively deflected through thesub-deflector to the four corners to detect positions of theposition-detection marks. Finally, the position errors are calculatedbased on the detected positions of the position-detection marks.

At a step S44, the errors of the relative positions of the fourposition-detection marks stored in the memory are subtracted from theposition errors, so that remaining position errors are calculated.

At a step S45, the deflection-efficiency-coefficients are calculatedbased on the remaining position errors. This ends the procedure.

The calculation of the deflection-efficiency-correction coefficients iscarried out as follows.

A correction of the sub-field may be made by using correctioncoefficients Gx, Gy, Rx, Ry, Hx, and Hy as follows.

    X'=Gx•X+Rx•Y+Hx•X•Y                (7)

    Y'=Ry•X+Gy•Y+Hy•X•Y                (8)

Here, X' and Y' are voltages applied to the sub-deflector, and X and Yare coordinates to which the charged-particle beam is to be deflected.The correction coefficients Gx, Gy, Rx, Ry, Hx, and Hy are obtained as amap in the main field to carry out the sub-deflector'sdeflection-efficiency correction.

In order to obtain the correction coefficients Gx, Gy, Rx, Ry, Hx, andHy, the following calculations are carried out. FIG. 32 is anillustrative drawing for explaining the calculations of the correctioncoefficients. Position errors detected at four corners A,. B, C, and Dof a rectangle having a side length L as shown in FIG. 32 are denoted as(δxa, δya), (δxb, δyb), (δxc, δyc), and (δxd, δyd), respectively. Thefollowing calculations are carried out first.

    δGx=(-δxa+δxb+δxc-δxd)/2L    (9)

    δGy=(-δya-δyb+δyc+δyd)/2L    (10)

    δRx=(-δxa-δxb+δxc-δxd)/2L    (11)

    δRy=(-δya+δyb+δyc-δyd)/2L    (12)

    δHx=(δxa-δxb+δxc-δxd)/L.sup.2 (13)

    δHy=(δya-δyb+δyc-δyd)/L.sup.2 (14)

Here, δGx, δGy, δRx, δRy, δHx, and δHy are differences between thecorrection coefficients used at present and the correction coefficientswhich should be used. These differences are added to the correctioncoefficients used at present as shown in the following equations toupdate the correction coefficients.

    Gx.sub.new =Gx.sub.old +δGx                          (15)

    Gy.sub.new =Gy.sub.old +δGy                          (16)

    Rx.sub.new =Rx.sub.old +δRx                          (17)

    Ry.sub.new =Ry.sub.old +δRy                          (18)

    Hx.sub.new =Hx.sub.old +δHx                          (19)

    Hy.sub.new =Hy.sub.old +δHy                          (20)

The equations (9) through (14) for obtaining the differences areapproximations derived by assuming that L is much greater than δx andδy. Thus, the measurement of the position errors and the updating of thecorrection coefficients are repeated until the position errors becomesufficiently small. Then, the correction coefficients thus obtained arestored as a map.

In the first embodiment of the fourth principle, the reference chiphaving a plurality of the position-detection marks is used, so that thecorrection coefficients for the entire main field are obtained throughstage movements equal to the number of the sub-fields. Therefore, thecorrection coefficients for the entire main field are obtained in ashort period of time. Also, the errors of the relative positions of theposition-detection marks may be measured in advance to cancel theseerrors at the time of obtaining the deflection efficiency. Thus, thecorrection coefficients are obtained in a short period of time at highprecision.

FIG. 33 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector according to a second embodiment of thefourth principle.

At a step S51, the reference chip 490 is placed on the stage 435 of thecharged-particle-beam exposure device 400.

At a step S52, position errors (differences between detected positionsand actual positions of the four position-detection marks) are measured.First, a center of the four position-detection marks is moved to acenter of a given sub-field, and the charged-particle beam is deflectedthrough the main deflector to the center of the sub-field. Then, thecharged-particle beam is successively deflected through thesub-deflector to the four corners to detect positions of theposition-detection marks. Finally, the position errors are calculatedbased on the detected positions of the position-detection marks.

At a step S53, errors of the relative positions of the fourposition-detection marks are measured by successively shifting thereference chip 490 through stage movement while keeping thecharged-particle beam at a fixed position.

At a step S54, the errors of the relative positions of the fourposition-detection marks are subtracted from the position errors, sothat remaining position errors are calculated.

At a step S55, the deflection-efficiency-correction coefficients arecalculated based on the remaining position errors. This ends theprocedure.

In the second embodiment of the fourth principle, the errors of therelative positions of the four position-detection marks are eliminatedby using the position-detection mechanism through the stage movement inthe charged-particle-beam exposure device. Thus, the correctioncoefficients are quickly obtained at a high precision without usinganother position detecting device.

FIG. 34 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector according to a third embodiment of thefourth principle.

At a step S61, the reference chip 490 is placed on the stage 435 of thecharged-particle-beam exposure device 400.

At a step S62, position errors (differences between detected positionsand actual positions of the four position-detection marks) are measured.First, a center of the four position-detection marks is moved to acenter of a given sub-field, and the charged-particle beam is deflectedthrough the main deflector to the center of the sub-field. Then, thecharged-particle beam is successively deflected through thesub-deflector to the four corners to detect positions of theposition-detection marks. Finally, the position errors are calculatedbased on the detected positions of the position-detection marks.

At a step S63, the deflection-efficiency-correction coefficients arecalculated from the position errors.

At a step S64, errors of the relative positions of theposition-detection marks contained in the obtaineddeflection-efficiency-correction coefficients are measured by using oneposition-detection mark. First, the position-detection mark is moved toa center of the main field, and the charged-particle beam is deflectedthrough the main deflector to the center of the main field. Next, thecharged-particle beam is deflected through the sub-deflector to a cornerof the sub-field, and, then, is deflected back to the center through themain deflector to detect a position of the position-detection mark. Thesame procedure is carried out for all the four corners of the sub-field.In this manner, the errors of the relative positions of the fourposition-detection marks contained in the position errors measured atthe step S62 are obtained by using the main deflector as a reference.

At a step S65, the deflection-efficiency-correction coefficients aremodified based on the errors of the relative positions of the fourposition-detecion marks. This ends the procedure.

In the third embodiment of the fourth principle, the errors of therelative positions of the position-detection marks are eliminated byusing one position-detection mark and the deflection amount of thesub-deflector as a reference. Thus, the precise correction coefficientsare quickly obtained through a simple method.

FIG. 35 is a flowchart of a process of correcting the deflectionefficiency of the sub-deflector according to an embodiment of the fifthprinciple.

At a step S71, a position-detection mark is moved through stage movementto one of 21×21 measurement points in the main field having 20×20sub-fields.

At a step S72, position errors are measured by deflecting thecharged-particle beam through the sub-deflector from centers of foursurrounding sub-fields to a position of the position-detection mark.First, the charged-particle beam is deflected through the main deflectorto a center of one of the four surrounding sub-fields. Then, thecharged-particle beam is deflected through the sub-deflector to theposition-detection mark to detect the position-detection mark, and adetected position error is recorded. The same procedure is carried outfor all the four surrounding sub-fields.

At a step S73, a check is made whether the measurements are made for allthe 21×21 measurement points. If there are one or more remainingmeasurement points to be measured, the procedure goes back to the stepS71 to repeat the above steps for the next measurement point. If thereis no remaining measurement point, the procedure proceed to a step S74.

At the step S74, the deflection-efficiency-correction coefficients arecalculated for all the measurement points based on the position errors.This ends the procedure.

In the embodiment of the fifth principle, the position-detection mark ismoved through stage movement only once for each of the measurementpoints when the correction coefficients are to be obtained for each ofthe sub-fields. This utilizes the fact that a plurality of sub-fieldsshare the measurement points as corners thereof. Namely, the correctioncoefficients for the entire main field are obtained through stagemovements equal to the number of the measurement points. Thus, thecorrection coefficients are obtained taking a short period of time.

As described above, according to the fourth principle of the presentinvention, use of the reference chip having a plurality ofposition-detection marks makes it possible to collect the correctiondata for a plurality of points by requiring only one stage movement.Thus, the correction data is obtained in a short period of time.

Also, according to the fourth principle of the present invention, thecorrection coefficients for the entire main field are obtained throughstage movements equal to the number of the sub-fields. Thus, thecorrection coefficients for the entire main field are obtained taking ashort period of time.

Also, according to the fourth principle of the present invention, theerrors of the relative positions of the position-detection marks can beeliminated by measuring these errors in advance. Thus, the correctioncoefficients are obtained at high precision in a short period of time.

Also, according to the fourth principle of the present invention, theerrors of the relative positions of the position-detection marks aremeasured by using the position detecting mechanism of thecharged-particle-beam exposure device. Thus, the correction coefficientsare obtained at high precision in a short period of time withoutrequiring another position detection device. Here, the positiondetecting mechanism of the charged-particle-beam exposure device may bea mechanism of the stage movement, which can be used as a measure fordetecting the relative positions of the position-detection marks.

Also, according to the fourth principle of the present invention, thecorrection coefficients may be corrected by using the deflection amountof the main deflector as a reference. Thus, the precise correctioncoefficients are quickly obtained through a simple method.

Also, according to the fourth principle of the present invention, theerrors of the relative positions of the position-detection markscontained in the correction coefficients are eliminated by using oneposition-detection mark and the deflection amount of the deflector as areference. Thus, the precise correction coefficients are quicklyobtained through a simple method.

Furthermore, according to the fifth principle of the present invention,the position-detection mark is moved through stage movement only oncefor each of the measurement points when the correction coefficients areto be obtained for each of the sub-fields. This utilizes the fact that aplurality of sub-fields share the measurement points as corners thereof.Namely, the correction coefficients for the entire main field areobtained through stage movements equal to the number of the measurementpoints. Thus, the correction coefficients are obtained taking a shortperiod of time.

Consequently, according to the fourth and fifth principles of thepresent invention, highly precise beam calibration is carried out in ashort period of time. Thus, the fourth and fifth principles of thepresent invention can greatly contribute to the development of thesemiconductor exposure technology.

Moreover, there are other problems concerning the present invention, andthese problems will be described below.

With recent advancement in the circuit density of integrated circuits,there has been a shift in use of technology for patterning semiconductorwafers from the photolithography technique widely used for a long tineto the charged-particle-beam exposure technique employing such beam asan electron beam.

The charged-particle-beam exposure technique includes thevariable-rectangle technique and the block exposure technique classifiedaccording to a pattern shape formed by one beam shot. In the blockexposure technique, a charged-particle beam passes through a mask havingunit patterns, so that even a complex pattern can be exposed at oneshot. These unit patterns are generally the patterns which repeatedlyappear on one chip. Thus, the block exposure technique is particularlyuseful for 256-Mbit DRAM chips, for example, because most areas of thechip has repetitive basic patterns despite micro structure thereof.Also, there is a technique called the BAA (blanking aperture array)technique. The BAA technique uses a BAA having apertures arrangedtherethrough in a matrix form, apertures being provided with a pair ofelectrodes. By switching on/off the voltage applied to the electrodes,each of the charged-particle beams passing through the apertures isindependently turned on/off to form a pattern.

FIG. 36 is an illustrative drawing showing a configuration of an exampleof the charged-particle-beam exposure device using the block exposuretechnique. The electron-beam exposure device includes an electron-beamgun 501, an electron-lens system L1a, a rectangular-hole plate 502, anelectron-lens system L1b, a beam shaping deflector 503, a first maskdeflector MD1, a dynamic-mask-focus coil DF, an electron-lens systemL2a, a mask stage 505 carrying a block mask 504, an electron-lens systemL2b, a third mask deflector MD3, a blanking deflector 506, a fourth maskdeflector MD4, a convergence-electron-lens system L3, a round aperture507, a projection-electron-lens system L4, a main deflector 508, asub-deflector 509, a projection-electron-lens system L5, a wafer stage511 carrying a wafer 510, and a control system. The control systemincludes a CPU 521, a clock unit 522 generating various clocks includingan exposure clock, a buffer memory 523, a control unit 524, adata-correction unit 525, a mask memory 526, and a main-deflectorsetting unit 527. The CPU 521 controlling operations of the entiredevice is connected to a clock unit 522, a mask memory 526, and amain-deflector setting unit 527 via a bus 528. In the figure, thedata-correction unit 525 and the main-deflector setting unit 527 areshown as including a digital-to-analog converting function and anamplifying function for convenience. A laser interferometer formeasuring a position of the wafer stage 511 and a stage-movementmechanism for shifting the wafer stage 511 are disclosed in U.S. Pat.Nos. 5,173,582 and 5,194,741, respectively, for example. Thus, these arenot shown in the figure, and a description thereof will be omitted.

An electron beam emitted from the electron-beam gun 501 passes throughthe rectangular-hole plate 502, and is deflected by the first maskdeflector MD1 and the second mask deflector MD2 to a desired pattern onthe block mask 504. The electron beam having a cross-sectional shape ofthe desired pattern is brought back to the optical axis through focusingfunctions of the electron-lens system L2a and the electron-lens systemL2b and through deflection functions of the third mask deflector MD3 andthe fourth mask deflector MD4. Then, the electron beam having the crosssection converged through the convergence-electron-lens system L3 isdirected to the wafer 510 by the projection-electron-lens system L4 andthe projection-electron-lens system L5. In this manner, the desiredpattern is exposed on the wafer.

The buffer memory 523 stores exposure-pattern data regarding patterns tobe exposed on the wafer 510 and block data regarding mask patternsformed through the block mask 504. The exposure-pattern data includesmain-deflector data supplied to the main deflector 508. The mask memory526 includes relations between mask-pattern positions and deflectiondata measured prior to an exposure process, and includes correction dataused for correcting the deflection data supplied to the dynamic-maskstigmator DS and the dynamic-mask-focus coil DF.

The exposure-pattern data stored in the buffer memory 523 after beingread by the CPU 521 includes pattern-data codes PDC indicating which oneof the mask patterns on the block mask 504 is to be used for anexposure. The control unit 524 uses the pattern-data codes PDC to readfrom the mask memory 526 the deflection data for deflecting the electronbeam to a position of a selected mask pattern, and, then, supplies thedeflection data to the first through fourth deflector MD1 through MD4for selecting the pattern. The deflection data read from the mask memory526 is also provided for the data-correction unit 525. Here, the readingof the deflection data from the mask memory 526 is carried out based onan exposure clock generated by the clock unit 522.

The main-deflector setting unit 527 reads main-deflector data for themain deflector 508 from the buffer memory 523 based on a clock from theclock unit 522, and supplies the main-deflector data to the maindeflector 508. Deflection data for the sub-deflector 509, the beamshaping deflector 503, and the blanking deflector 506 is broken downinto shot data by the control unit 524 according to data stored in thebuffer memory 523. The shot data is supplied to the sub-deflector 509,the beam shaping deflector 503, and the blanking deflector 506 via thedata-correction unit 525. Namely, the control unit 524 determines a sizeof the electron beam and a position on the block mask 504 of theelectron beam according to the data stored in the buffer memory 523 tosupply the size and the position to the data-correction unit 525 whenthe variable-rectangle exposure is used. The data-correction unit 525corrects the deflection data of the electron beam for a pattern to beexposed based on the correction data read from the mask memory 526. Thedeflection data of the beam shaping deflector 503 determines the size ofthe variable rectangle of the electron beam, and the deflection data ofthe blanking deflector 506 is set for each shot of exposure.

FIG. 37 is an illustrative drawing showing an example of the block mask504. In the figure, the block mask 504 includes a substrate 504a made ofmetal or semiconductor like silicon and deflection areas 504-1 through504-12 formed on the substrate 504a. Each of the deflection areas 504-1through 504-12 has a plurality of mask patterns formed therein. In theelectron-beam exposure device using the block exposure, an area of themask patterns which can be selected by deflecting the electron beam froma predetermined position on the mask stage 505 is limited. Each of thedeflection areas 504-1 through 504-12 is a 5-mm square, for example,corresponding to this limit. When the mask patterns within thedeflection area 504-8 are to be exposed, for example, the mask stage 505is shifted such that the electron-optical-system axis of the deviceroughly coincides with a center of the deflection area 504-8.

As shown in an example of FIG. 37, the number of the mask patternsarranged in the deflection area 504-8 is 48. Each of the mask patternsis identified based on the pattern-data codes PDC. Namely, thepattern-data codes PDC are an indicator for reading data correspondingto a given mask pattern from the mask memory 526 by using an exposureclock of maximum 10 MHz, for example, provided from the clock unit 522.As described above, the mask memory 526 stores the relations between themask-pattern positions and the deflection data and the correction datato be supplied to the dynamic-mask stigmator DS and thedynamic-mask-focus coil DF for deflecting the electron beam to a givenmask pattern. The deflection data and the correction data for a givendeflection area are obtained by adjusting the electron beam prior to anexposure process, and are stored in the mask memory 526.

In order to conduct an exposure process at higher speed, a waiting timefor a shot, i.e., a time period required for deflecting the electronbeam, must be reduced. Although an illustrative description is omittedin FIG. 36, the deflection data is provided for the main deflector 508,etc., via amplifiers. Thus, a settling time of such amplifiers (a timeperiod required for the amplifiers to become stable) largely determinesthe waiting time for a shot. Therefore, it is desirable to reduce thewaiting time for a shot by reducing the settling time of suchamplifiers, so that a redundant time involved in the drawing of patternsis decreased in the electron-beam exposure device to boost thethroughput.

FIG. 38 is a block diagram of an exemplary driving unit of the maindeflector 508. In the figure, the deflection data from themain-deflector setting unit 527 is supplied to a driving system 610 viaa digital-to-analog converter (DAC) 601, a current-to-voltage converter(IV converter) 602, and a resistor 603. The driving system 610 includesa resistor 604, a resistor 605, a differential amplifier 606, and acapacitor 607. The main deflector 508 includes a coil 608 which is aninductor impedance.

In the driving unit of FIG. 38, there is a large delay in the feedbackbecause of the main deflector 508 comprising the coil 608. FIGS. 39Athrough 39C are time charts showing signals observed at various pointsof FIG. 38. When an input signal shown in FIG. 39A is applied to a nodeA of FIG. 38, for example, an output signal appearing at a node B wouldhave a ringing effect as shown in FIG. 39B if the capacitor 607 were notprovided.

In order to shorten the settling time of the output signal, thecapacitor 607 for preventing the ringing effect is connected in parallelwith the resistor 604 to lower the frequency range of the differentialamplifier 606. Namely, the existence of the capacitor 607 lowers afrequency characteristic of the differential amplifier 606 to reduce athrough rate.

The existence of the capacitor 607, however, makes a change in the inputof the differential amplifier 606 extremely slow, so that a signal asshown in FIG. 39C is observed as the output signal at the node B. Thiscreates a problem of a long settling time of the differential amplifier606. Because of this, the waiting time for a shot should be set inaccordance with this long settling time, thereby hindering an effort toenhance the throughput of the device.

Accordingly, there is a need for a charged-particle exposure devicewhich can shorten the settling time of the amplifier to reduce thewaiting time for a shot by suppressing the ringing effect of anamplifier output without lowering the frequency range of the amplifier.

FIG. 40 is an block diagram of a main part of a charged-particle-beamexposure device according to a first embodiment of a sixth principle ofthe present invention. In FIG. 40, the same elements as those of FIG. 38are referred to by the same numerals. In this embodiment, the sixthprinciple of the present invention is applied to an electron-beamexposure device, and a first embodiment of a charged-particle-beamexposure method is used in the device.

FIG. 40 shows a driving unit of the main deflector 508. In the figure,the deflection data from the main-deflector setting unit 527 is suppliedto the driving system 610 via the digital-to-analog converter 601, thecurrent-to-voltage converter 602, and the resistor 603. The drivingsystem 610 includes the resistor 604, the resistor 605, and thedifferential amplifier 606. The main deflector 508 includes the coil 608which is an inductor impedance. A node N connects the resistor 603, theresistor 604, a resistor 705, and a reverse input node of thedifferential amplifier 606 together. The other input node of thedifferential amplifier 606 is connected to a ground. A node D connectsthe resistor 604 and the resistor 605, and the coil 608 is interposedbetween the node D and the output node of the differential amplifier606.

A pulse generating circuit 701 generates a pulse signal having areversed phase to a first wave of the ringing appearing in the output ofthe differential amplifier 606 in order to cancel the first wave of theringing. The generation of the pulse signal is based on the deflectiondata provided from the main-deflector setting unit 527. The pulse signalis supplied to the differential amplifier 606 via the resistor 705. Apulse length of the pulse signal is shorter than a time period from astart of the first wave of the ringing to a start of the second wave ofthe ringing. The pulse generating circuit 701 includes a pulse-parameteroutputting circuit 702, a DAC 703, and an IV converter 704. Thepulse-parameter outputting circuit 702 generates pulse parameters tosuppress the ringing appearing at the node D based on the deflectiondata from the main-deflector setting unit 527. The pulse parameterinclude a pulse-delay time, a pulse length, a magnitude, etc., of thepulse signal generated by the pulse generating circuit 701. The pulseparameters are applied to a node C via the DAC 703 and the IV converter704. It is desirable to be able to set at least one of the pulseparameters, and, also, it is desirable to be able to set each of thepulse parameters independently from each other.

FIGS. 41A through 41D are time charts showing signals observed atvarious points of FIG. 40. FIG. 41A shows an input signal applied to thenode A of FIG. 40. FIG. 41B shows an output signal which would appear atthe node D if the pulse generating circuit 701 were not provided. FIG.41C shows a pulse signal generated by the pulse generating circuit 701and applied to the node C. FIG. 41D shows an output signal appearing atthe node D when the pulse generating circuit 701 is provided. In thefirst embodiment, the pulse signal appearing at the node C is added to asignal applied to the reverse input node of the differential amplifier606 to cancel the delayed response fed back to the differentialamplifier 606, so that the ringing shown in FIG. 41B is suppressed.Therefore, the differential amplifier 606 for an inductor impedance hasa shorter settling time without sacrificing the frequency characteristicof the differential amplifier 606.

FIG. 42 is a block diagram of a main part of a charged-particle-beamexposure device according to a second embodiment of the sixth principleof the present invention. In FIG. 42, the same elements as those of FIG.40 are referred to by the same numerals. In this embodiment, the sixthprinciple of the present invention is applied to an electron-beamexposure device, and a second embodiment of a charged-particle-beamexposure method is used in the device.

In FIG. 42, the deflection data is generated by a pattern generating(PG) unit 527A, and is supplied to the digital-to-analog converter 601and a pulse generating circuit 711. The pulse generating circuit 711includes a data-timing-adjustment circuit 712, a memory 713, a memory714, a clock generating circuit 715, the DAC 703, and the IV converter704. A clock supplied to the digital-to-analog converter 601 and theclock generating circuit 715 is provided from the clock unit 522 of FIG.36, for example. The DAC 703 is provided with a clock from the clockgenerating circuit 715. An output signal at the node D is supplied to acontrol unit 716 via a analog-to-digital converter (ADC) 717constituting a feedback-adjustment system. The control unit 716corresponds to the control unit 524 of FIG. 36, for example.

A change in the data from the pattern generating unit 527A from n-thdata to n+1-th data appears as a change in the output of thedifferential amplifier 606. The feedback of the voltage change at thenode D to the control unit 716 via the analog-to-digital converter 717makes it possible for the analog-to-digital converter 717 to monitor theoutput change of the differential amplifier 606. The control unit 716takes a derivation of the data fed back via the analog-to-digitalconverter 717, and obtains pulse parameters which make the derivationbecome zero in the shortest period of time. That is, the pulseparameters for suppressing the first wave of the ringing appearing atthe node D are obtained. In practice, the control unit 716 calculatesderivations of the data provided from the analog-to-digital converter717 while changing the pulse parameters, and obtains optimal values ofthe pulse parameters with which the derivation becomes zero the fastest.When obtaining the optimal values of the pulse parameters, the controlunit 716 supplies pulse parameters regarding the pulse delay and thepulse length to the clock generating circuit 715, and supplies a pulseparameter concerning the pulse magnitude to the DAC 703.

The optimal pulse parameters obtained by the control unit 716 are storedin the memories 713 and 714 at addresses indicated by the data changefrom the n-th data to the n+1-th data provided from the patterngenerating unit 527A. Here, the optimal pulse parameters regarding thepulse delay and the pulse length are stored in the memory 713, and theoptimal pulse parameter regarding the pulse magnitude is stored in thememory 714. The storing of the optimal pulse parameters in the memories713 and 714 is carried out for three types of data changes. The optimalpulse parameters for other data changes are obtained based on anapproximation function δ_(para) derived from the optimal pulseparameters for the three types of data changes.

    δ.sub.para =P(X.sub.n+1 -X.sub.n)×Q(X.sub.n)   (21)

In the equation (21), P is a function of a jump amount of the data, andQ is a linear interpolation function.

Namely, the pulse parameters are proportional to a change in the inputdata, i.e., a difference in the data or the jump amount of the data, andreceives an effect of the jump-start point X_(n) as a correction by amultiplication form. Q(X_(n)) is a linear interpolation function havingvalues equal to monitored values at points monitored by the control unit716. Based on the approximation function δ_(para), the optimal pulseparameters are obtained for every possible input-data change, i.e.,every possible jump amount. Then, the optimal pulse parameters arefinely adjusted by repeating the same procedure as that of havingobtained the optimal pulse parameters the first time. Therefore, theoptimal pulse parameters for every possible input-data change areobtained in a relatively short period of time.

An operation at a time of exposure will be described below. Thedeflection data provided from the pattern generating unit 527A for then+1-th pattern data is supplied as a data change from the n-th data tothe n+1-th data to the differential amplifier 606 via thedigital-to-analog converter 601, the current-to-voltage converter 602,and the resistor 603. The data-timing-adjustment circuit 712 adjusts thedata timing of the n-th data and the n+1-th data to provide themsimultaneously for the memories 713 and 714 as addresses thereof. Inthis manner, the pulse parameters regarding the pulse delay and thepulse length are read from the memory 713 to be supplied to the clockgenerating circuit 715. Also, the pulse parameter regarding the pulsemagnitude is read from the memory 714 to be supplied to the DAC 703.

FIG. 43 is a block diagram of an example of the data-timing-adjustmentcircuit 712 shown with the memory 713 and the memory 714. In the figure,the memory 713 and the memory 714 are shown as one memory forconvenience of explanation. The data-timing-adjustment circuit 712includes a register 712A, so that the n-th data temporarily stored inthe register 712A is supplied to the memory at the same time as then+1-th data is supplied.

The clock generating circuit 715 generates a clock in response to aclock synchronizing with the n+1-th data from the clock unit 522 basedon the pulse parameters regarding the pulse delay and the pulse lengthread from the memory 713. The generated clock is sent to the DAC 703.The pulse parameter regarding the pulse magnitude read from the memory714 is supplied to the DAC 703 as weighting data. An output of the DAC703 is provided for the node N via the IV converter 704 and the resistor705 to be added to an output of the digital-to-analog converter 601provided via the current-to-voltage converter 602 and the resistor 603.A signal after the addition is supplied to the reverse input node of thedifferential amplifier 606.

FIG. 44A is a time chart showing a clock provided from the clock unit522 to the digital-to-analog converter 601 and the clock generatingcircuit 715. FIG. 44B is a time chart showing an output signal observedat the node D when the pulse generating circuit 711 is not provided.FIG. 44C is a time chart showing a clock provided from the clockgenerating circuit 715 to the DAC 703. FIG. 44D is a time chart showinga correction pulse signal output from the IV converter 704.

FIGS. 45A and 45B are time charts showing output voltages obtainedthrough a simulation. FIG. 45A shows an output voltage obtained at thenode D when the pulse generating circuit 711 for applying the correctionpulse signal to the node N is not provided. FIG. 45B shows an outputvoltage obtained at the node D when the pulse generating circuit 711 isprovided to apply the correction pulse signal to the node N. As shown inFIGS. 45A and 45B, the ringing of the output voltage is suppressedaccording to the second embodiment of the sixth principle of the presentinvention.

FIG. 46 is a flowchart of a process of obtaining the optimal pulseparameters. The process of obtaining the optimal pulse parameters willbe described with reference to FIG. 46 and FIG. 42.

At a step S81, the deflection data generated by the pattern generatingunit 527A is supplied to the differential amplifier 606 via thedigital-to-analog converter 601, the current-to-voltage converter 602,and the resistor 603.

At a step S82, the pulse delay and the pulse magnitude are set in thepulse generating circuit 711 by the control unit 716.

At a step S83, the pulse generating circuit 711 generates a correctionpulse signal based on the pulse parameters set at the step S82.

At a step S84, the control unit 716 monitors an output signal appearingat the node D via the analog-to-digital converter 717.

At a step S85, the control unit 716 measures the settling time of themonitored output signal.

At a step S86, the control unit 716 checks whether the correction pulsesignal is generated by the pulse generating circuit 711 for all thepulse magnitudes and the pulse delays. If the answer is yes, theprocedure goes to a step S87. Otherwise, the procedure goes back to thestep S82.

At the step S87, the control unit 716 obtains the pulse magnitude andthe pulse delay of the shortest settling time.

At a step S88, the control unit 716 checks whether sufficient data forobtaining the approximation function δ_(para) is collected. If it isnot, the procedure goes back to the step S81. Otherwise, the proceduregoes to a step S89.

At the step S89, the control unit 716 obtains the approximation functionδ_(para) by using the collected data.

At a step S90, the control unit 716 obtains pulse parameters regardingthe pulse magnitude, the pulse delay, and the pulse length for all thedeflection data (deflection pattern).

At a step S91, the control unit 716 stores the obtained pulse parametersin the memories 713 and 714. This ends the procedure.

FIG. 47 is a block diagram of a main part of a charged-particle-beamexposure device according to a third embodiment of the sixth principleof the present invention. In FIG. 47, the same elements as those of FIG.42 are referred to by the same numerals, and a description thereof willbe omitted. In this embodiment, the sixth principle of the presentinvention is applied to an electron-beam exposure device, and a thirdembodiment of a charged-particle-beam exposure method is used in thedevice.

In FIG. 47, the feedback adjustment system includes a error-band settingcircuit 722 for setting an error-band width based on an instructiongiven by the control unit 716, and, also, includes a window comparator721. The window comparator 721 compares the output signal obtained fromthe node D with the error-band width obtained from the error-bandsetting circuit 722 to generate a signal indicating whether the outputsignal falls in the error-band width. This signal is supplied to thecontrol unit 716. The control unit 716 changes the pulse parameters toobtain the shortest time period from a start of a change in the outputsignal (voltage) at the node D to a time when the output signal fallswithin the error-band width. At the same time, the control unit 716continues the feedback operation through the window comparator 721 toobtain the optimal pulse parameters. Other operations are the same asthose of the second embodiment of the sixth principle described withreference to FIG. 42.

FIG. 48 is a flowchart of a process of obtaining the optimal pulseparameters according to the third embodiment of the sixth principle.This process of obtaining the optimal pulse parameters will be describedwith reference to FIG. 48 and FIG. 47.

At a step S101, the control unit 716 sends an instruction to theerror-band setting circuit 722 to set an error-band width.

At a step S102, the deflection data generated by the pattern generatingunit 527A is supplied to the differential amplifier 606 via thedigital-to-analog converter 601, the current-to-voltage converter 602,and the resistor 603.

At a step S103, the pulse delay and the pulse magnitude are set in thepulse generating circuit 711 by the control unit 716.

At a step S104, the pulse generating circuit 711 generates a correctionpulse signal based on the pulse parameters set at the step S103.

At a step S105, the control unit 716 monitors a signal obtained from thewindow comparator 721.

At a step S106, the control unit 716 measures the settling time of themonitored signal, i.e., measures a time period passing before the outputsignal at the node D falls within the error-band width.

At a step S107, the control unit 716 checks whether the correction pulsesignal is generated by the pulse generating circuit 711 for all thepulse magnitudes and the pulse delays. If the answer is yes, theprocedure goes to a step S108. Otherwise, the procedure goes back to thestep S103.

At the step S108, the control unit 716 obtains the pulse magnitude andthe pulse delay of the shortest settling time.

At a step S109, the control unit 716 checks whether sufficient data forobtaining the approximation function δ_(para) is collected. If it isnot, the procedure goes back to the step S102. Otherwise, the proceduregoes to a step S110.

At the step S110, the control unit 716 obtains the approximationfunction δ_(para) by using the collected data.

At a step S111, the control unit 716 obtains pulse parameters regardingthe pulse magnitude, the pulse delay, and the pulse length for all thedeflection data (deflection pattern).

At a step S112, the control unit 716 stores the obtained pulseparameters in the memories 713 and 714. This ends the procedure.

FIG. 49 is a block diagram of a main part of a charged-particle-beamexposure device according to a fourth embodiment of the sixth principleof the present invention. In FIG. 49, the same elements as those of FIG.42 are referred to by the same numerals, and a description thereof willbe omitted. In this embodiment, the sixth principle of the presentinvention is applied to an electron-beam exposure device, and a fourthembodiment of a charged-particle-beam exposure method is used in thedevice.

In FIG. 49, the feedback adjustment system includes a reflectiondetector 731 detecting electrons of the electron beam scattered by thewafer 510, an amplifier 732 amplifies a detected signal of thereflection detector 731, and an ADC 733 converting an output of theamplifier 732 to digital data to be supplied to the control unit 716.The control unit 716 monitors movement of the electron beam based on thedigital data provided from the ADC 733. In the same manner as in thesecond embodiment of the sixth principle, the control unit 716 takes aderivation of the digital data sent from the ADC 733 while changing aposition of the electron beam, so as to obtain the optimal pulseparameters with which the derivation becomes zero in the shortest periodof time. When obtaining the optimal pulse parameters, the control unit716 supplies the pulse parameters regarding the pulse delay and thepulse length to the clock generating circuit 715, and supplies the pulseparameter regarding the pulse magnitude to the DAC 703 Other operationsare the same as those of the second embodiment of the sixth principledescribed with reference to FIG. 42.

FIG. 50 is a flowchart of a process of obtaining the optimal pulseparameters according to the fourth embodiment of the sixth principle.This process of obtaining the optimal pulse parameters will be describedwith reference to FIG. 50 and FIG. 49.

At a step S121, the deflection data generated by the pattern generatingunit 527A is supplied to the differential amplifier 606 via thedigital-to-analog converter 601, the current-to-voltage converter 602,and the resistor 603.

At a step S122, the pulse delay and the pulse magnitude are set in thepulse generating circuit 711 by the control unit 716.

At a step S123, the pulse generating circuit 711 generates a correctionpulse signal based on the pulse parameters set at the step S122.

At a step S124, the control unit 716 uses the reflection detector 731 todetect the scattered electrons while changing a position of the electronbeam.

At a step S125, the control unit 716 monitors a detected signal of thereflection detector 731 via the amplifier 732 and the ADC 733.

At a step S126, the control unit 716 measures the settling time of themonitored detected signal.

At a step S127, the control unit 716 checks whether the correction pulsesignal is generated by the pulse generating circuit 711 for all thepulse magnitudes and the pulse delays. If the answer is yes, theprocedure goes to a step S128. Otherwise, the procedure goes back to thestep S122.

At the step S128, the control unit 716 obtains the pulse magnitude andthe pulse delay of the shortest settling time.

At a step S129, the control unit 716 checks whether sufficient data forobtaining the approximation function δ_(para) is collected. If it isnot, the procedure goes back to the step S121. Otherwise, the proceduregoes to a step S130.

At the step S130, the control unit 716 obtains the approximationfunction δ_(para) by using the collected data.

At a step S131, the control unit 716 obtains pulse parameters regardingthe pulse magnitude, the pulse delay, and the pulse length for all thedeflection data (deflection pattern).

At a step S132, the control unit 716 stores the obtained pulseparameters in the memories 713 and 714. This ends the procedure.

The above description of the sixth principle has been provided throughan example in which the deflector is an electromagnetic deflector suchas a main deflector. However, the sixth principle of the presentinvention can be applied to any types of deflectors as well as anelectromagnetic deflector and a main deflector.

FIGS. 51A and 51B are circuit diagrams showing configurations of thedynamic-mask stigmator DS of FIG. 36. FIG. 51A shows a configuration ofan X-axis portion of the dynamic-mask stigmator DS, and FIG. 51B shows aconfiguration of a Y-axis portion of the dynamic-mask stigmator DS.

In FIG. 51A, the X-axis portion of the dynamic-mask stigmator DS has astigmator coil portion including coils LX1 through LX4, each comprising40 turns, for example. The data having 12 bits, for example, is suppliedvia a DAC 741 and an amplifier 742 to the coils LX1 through LX4connected in a series. In FIG. 51B, the Y-axis portion of thedynamic-mask stigmator DS has a stigmator coil portion including coilsLY1 through LY4, each comprising 40 turns, for example. The data having12 bits, for example, is supplied via a DAC 751 and an amplifier 752 tothe coils LY1 through LY4 connected in a series. Settling times of theamplifiers 742 and 752 supplying the data to the dynamic-mask stigmatorDS are mainly determined by the load of the dynamic-mask stigmator DS.Namely, the settling time of the amplifiers 742 and 752 are dependent onvarious parameters of the coils LX1 through LX4 and the coils LY1through LY4 such as the diameter, the number of turns (laps) determiningthe self-inductance, and a mutual inductance determining a mutualdependency between the coils.

The load amount of the coils is basically determined by configurationsof the beam-deflection system and the lens system, so that the loadamount cannot be freely reduced to shorten the settling time of theamplifiers 742 and 752. FIGS. 52A through 52D are charts showing theringing of the output signal of the amplifier 742 for various turnnumbers of the coils LX1 through LX4. FIG. 52A shows the output signalof the amplifier 742 when the turn number is 0, i.e., the coils areshort-circuited. FIGS. 52B through 52D show cases in which the turnnumber is 20, 30, and 40, respectively. As shown in the figures, theringing of the output signal of the amplifier 742 increases as the turnnumber increases to raise the load amount.

FIG. 53 is a circuit diagram of the dynamic-mask-focus coil DF of FIG.36.

In FIG. 53, a focus coil portion of the dynamic-mask-focus coil DFinclude a coil LF having 40 turns, for example. The data having 12 bits,for example, is supplied via a DAC 761 and an amplifier 762 to the coilLF. A settling time of the amplifier 762 supplying the data to thedynamic-mask-focus coil DF is mainly determined by the load of thedynamic-mask-focus coil DF. Namely, the settling time of the amplifier762 is dependent on various parameters of the coil LF such as thediameter, the number of turns (laps) determining the self-inductance,and a mutual inductance determining a mutual dependency between thecoils.

The load amount of the coils is basically determined by configurationsof the beam-deflection system and the lens system, so that the loadamount cannot be freely reduced to shorten the settling time of theamplifier 762.

However, it is possible to add the correction pulse signal of the aboveembodiments of the sixth principle to the input of the amplifiers sothat the ringing of the output signals of the amplifiers 742, 752, and762 is suppressed to shorten the settling time.

Also, in order to shorten the settling time of the amplifiers, theeffective load of the coils can be suppressed as shown in the followingembodiments.

FIG. 54 is a circuit diagram of a main part of a charged-particle-beamexposure device according to a first embodiment of a seventh principle.In FIG. 54, the same elements as those of FIGS. 51A and 51B are referredby the same numerals, and a description thereof will be omitted. In thisembodiment, the seventh principle is applied to an electron-beamexposure device, and a first embodiment of a charged-particle-beamexposure method is used in the device.

FIG. 54 shows a stigmator-coil portion DSx1 through DSxN for the X axisof the dynamic-mask stigmator DS. A drawing for a stigmator-coil portionDSy1 through DSyN for the Y axis of the dynamic-mask stigmator DS is thesame as FIG. 52, and is thus omitted. The stigmator-coil portion DSx1for the X axis of the dynamic-mask stigmator DS includes coils LX1-1through LX4-1, each comprising 40 turns, for example. Data having 12bits, for example, is supplied via a DAC 741-1 and a amplifier 742-1 tothe coils LX1-1 through LX4-1 arranged in a series. In the same manner,data having 12 bits is supplied via a DAC 741-2 and a amplifier 742-2 tocoils LX1-2 through LX4-2 arranged in a series. The coils LX1-2 throughLX4-2 constitute the stigmator-coil portion DSx2. Also, data having 12bits is supplied via a DAC 741-N and a amplifier 742-N to coils LX1-Nthrough LX4-N arranged in a series. The coils LX1-N through LX4-Nconstitute the stigmator-coil portion DSx2.

In FIG. 54, even when the same amplifiers are used for the amplifiers742-1 through 742-N of different stages, an output of each amplifierwill have some drift depending on temperature. Namely, because ofthermal-condition changes and the like caused by changes in the ambienttemperature and heat generation of the amplifiers, outputs of theamplifiers have some drift. Therefore, when a plurality of stages of thestigmator-coil portions are arranged along the axis of the electronbeam, the electron beam passing through the round aperture 507 will havea variation in the current density and will be blurred.

FIG. 55 is a chart showing a variation in the current density of theelectron beam passing through the round aperture 507 when a position ofthe electron beam is displaced by the drift in the output of theamplifiers. As shown in FIG. 55, in order to keep the variation of thecurrent density within a 1-% range, the electron beam must be positionedwith an extreme precision. In this embodiment, thus, two stigmator-coilportions adjacent to each other (e.g, DSx1 and DSx2) are driven byelectric currents of opposite directions, as shown by arrows in FIG. 54.

FIG. 56 is a chart showing a drift in an output of an amplifier. Asshown in the figure, the drift increases over time in a negativedirection when a current of a positive direction is applied. When acurrent of a negative direction is applied, the drift increases overtime in a negative direction as well. Therefore, when every twostigmator-coil portions adjacent to each other are driven by electriccurrents of opposite directions, the drifts in the outputs of theamplifiers are canceled with each other.

FIG. 57 is an illustrative drawing showing an example of a configurationof the stigmator-coil portions when six of them are provided. Each ofthe stigmator-coil portions DSx1 through DSx6 has a diameter of 15 mmand a length of 4 mm along the electron-beam axis, and is arranged at a0.8-mm interval. A total length from the stigmator-coil portion DSx1 tothe stigmator-coil portion DSx6 along the electron-beam axis is 28 mm.

A configuration of the stigmator-coil portions DSy1 through DSyN for theY axis of the dynamic-mask stigmator DS is the same as that of FIG. 57,except that they are arranged with a phase displacement of 450 relativeto the stigmator-coil portions DSx1 through DSxN around theelectron-beam axis.

In the first embodiment of the seventh principle, four coils areprovided. However, the number of coils can be 2 or more than 4, as longas the coils are arranged such that magnetic fields generated by thecoils are canceled at a center position between the coils.

FIG. 58 is a circuit diagram of a main part of a charged-particle-beamexposure device according to a second embodiment of the seventhprinciple. In FIG. 58, the same elements as those of FIG. 53 arereferred by the same numerals, and a description thereof will beomitted. In this embodiment, the seventh principle is applied to anelectron-beam exposure device, and a second embodiment of acharged-particle-beam exposure method is used in the device.

FIG. 58 shows a focus-coil portion of the dynamic-mask-focus coil DF.The focus-coil portion of the dynamic-mask-focus coil DF includes coilsLF1 through LFN, each comprising 40 turns, for example. Data having 12bits, for example, is supplied via a DAC 761-1 and an amplifier 762-1 tothe coil LF1. In the same manner, data having 12 bits is supplied via aDAC 761-2 and an amplifier 762-2 to the coil LF2. The coil LF2constitutes the focus-coil portion. Also, data having 12 bits issupplied via a DAC 761-N and an amplifier 762-N to the coil LFN. Thecoil LFN constitutes the focus-coil portion.

In FIG. 58, even when the same amplifiers are used for the amplifiers762-1 through 762-N of different stages, an output of each amplifierwill have some drift depending on temperature. Namely, because ofthermal-condition changes and the like caused by changes in the ambienttemperature and heat generation of the amplifiers, outputs of theamplifiers have some drift. Therefore, when a plurality of stages of thefocus-coil portions are arranged along the axis of the electron beam,the electron beam passing through the round aperture 507 will have avariation in the current density and will be blurred.

FIG. 59 is a chart showing a variation in the current density of theelectron beam passing through the round aperture 507 when a position ofthe electron beam is displaced by the drift in the output of theamplifiers. As shown in FIG. 59, in order to keep the variation of thecurrent density within a 1-% range, the electron beam must be positionedwith an extreme precision. In this embodiment, thus, two focus-coilportions adjacent with each other (e.g, LF1 and LF2) are driven byelectric currents of opposite directions, as shown by arrows in FIG. 59.

FIGS. 60A and 60B are illustrative drawings showing an example of aconfiguration of the focus-coil portions when five of them are provided.FIG. 60A shows the focus-coil portion of the dynamic-mask-focus coil DFof the electron-beam exposure device, and FIG. 60B shows an enlargedview of the configuration of the focus-coil portions of thedynamic-mask-focus coil DF. FIG. 60B also shows a magnetic field Bdistributed along the electron-beam axis of the electron-lens systemL2a. Each of focus coils LF1 through LF5 has a 5-mm diameter φ, and isarranged at a 5-mm interval P. A total length TL from the focus coil LF1to the focus coil LF5 along the electron-beam axis of the electron-beamexposure device is 20 mm. In this configuration, the interval P must belarger than or equal to the diameter φ.

In the first and second embodiments of the seventh principle of thepresent invention, the correction pulse signal may be added to the inputof each amplifier as in the first through fourth embodiments of thesixth principle. In this case, an adverse effect of the drift in theoutput of the amplifier is reduced, and, at the same time, an adverseeffect of the ringing of the output of the amplifier is alleviated.

Applications of the sixth and seventh principles of the presentinvention are not limited only to electron-beam exposure devices. Thesixth and seventh principles of the present invention can be applied toany charged-particle-beam exposure devices.

According to the sixth principle of the present invention, the pulsesignal is added to the input of the amplifier to cancel the delayedresponse fed back to the amplifier, thereby suppressing the ringing.Therefore, an amplifier having a short settling time used for inductorimpedance is provided without sacrificing the frequency characteristicsof the amplifier.

According to the sixth principle of the present invention, the optimalpulse parameters for the correction pulse signal are stored in memories,and the pulse signal is generated based on the optimal pulse parameters.Therefore the ringing is suppressed by using a simple circuit structure.

According to the seventh principle of the present invention, the use ofa plurality of stages of coils enables a reduction in the effective loadof the coils, and enables a cancellation of the drift in the output ofthe amplifier. Therefore, the settling time of the amplifier isshortened.

Accordingly, the charged-particle-beam exposure device according to thesixth and seventh principles of the present invention can shorten thesettling time of the amplifier to reduce the waiting time for a shot bysuppressing the ringing effect of an amplifier output without loweringthe frequency range of the amplifier.

Moreover, there are other problems of concern to the present invention,and these problems will be described below.

FIG. 61 is an illustrative drawing showing a configuration of acharged-particle-beam exposure device of the related art using a stencilmask.

A charged-particle beam (e.g., electron beam) emitted from acharged-particle gun 810 passes through a selected hole pattern formedthrough a stencil mask 812 so that a cross section of the beam is shapedin a selected pattern. The beam having the shaped cross section isconverged and positioned on a wafer (not shown). FIG. 61 shows a beamaxis AX and a beam trajectory 813A. The charged-particle-beam exposuredevice of FIG. 61 also includes electromagnetic lenses 821A, 821B, 822A,822B, and 823 and aperture plates 830 and 831.

The charged-particle beam passing through electromagnetic lens 821Balong the beam axis AX is deflected by a deflector 845, and, then, bentby a deflector 846 to become parallel to the beam axis AX. In thismanner, the charged-particle beam runs in a vertical direction when itpasses through the selected hole pattern of the stencil mask 812. Thecharged-particle beam having passed through the stencil mask 812 isdeflected by a deflector 847 and bent by a deflector 848 to be placedalong the beam axis AX.

In the charged-particle-beam exposure device of this configuration, thecharged-particle beam is incident to the stencil mask 812 from a normaldirection, so that the cross section of the beam is shaped with highprecision. Also, a hole pattern of the stencil mask 812 can be selectedfrom a wide-range area.

However, when a deflection amount of any of the deflectors 845 through848 is changed, there is a huge positional displacement of thecharged-particle beam on the aperture plate 831 and on the wafer. Thiscrates a problem when a hole pattern of the stencil mask 812 isselected. When the deflection amount of the deflector 846 is slightlyincreased, for example, the charged-particle beam has a beam trajectory813B as shown in FIG. 61. A high precision such as within a range of0.01 μm, for example, is required for the positioning of thecharged-particle beam on the wafer. When a hole pattern is selected, thedeflectors 845 through 848 receive driving voltages having a stepchange. In this case, a long settling time is required.

In order to precisely direct the charged-particle beam at a targetposition on the wafer, the charged-particle beam is blanked during thesettling time by a blanking deflector (not shown) and the aperture plate831. A beam exposure on the wafer should wait until the settling timelapses, thereby creating a dead time to reduce throughput of theexposure process.

FIG. 62 is an illustrative drawing showing a configuration of acharged-particle-beam exposure device disclosed in Japanese PatentLaid-Open Application No.62-206828.

In the device of FIG. 62, cross-over images CO1 and CO2 of a gun crossover CO of the charged-particle gun 810 are positioned between theelectromagnetic lens 821B and an electromagnetic lens 822 and positionedbetween the electromagnetic lens 822 and the electromagnetic lens 823. Adeflector 840 is arranged such that a center point thereof is positionedat a position of the cross-over image CO1. Also, a deflector 849 isarranged such that a center point thereof is positioned at a position ofthe cross-over image CO2. A path 813C shows an extent of thecharged-particle beam, enlarged in a direction perpendicular to the beamaxis AX, passing through the electromagnetic lenses 821B, 822, and 823when the deflection amount of the deflectors 840 and 849 is zero.

The charged-particle beam deflected by the deflector 840 to pass througha selected hole pattern of the stencil mask 812 is focused at a positionof the cross-over image CO2 through a convergence effect of theelectromagnetic lens 822. The charged-particle beam is then deflected bythe deflector 849 to run along the beam axis AX.

In the charged-particle-beam exposure device of FIG. 62, deflectorsfunctionally equivalent to the deflectors 846 and 847 are not provided.Thus, a range in which a hole pattern of the stencil mask 812 can beselected becomes narrower than that of FIG. 61.

In FIG. 62, the cross-over image CO2 is positioned several millimetersfrom the top of the electromagnetic lens 823. Because of such a shortdistance, the center point of the deflector 849 cannot be positioned atthe position of the cross-over image CO2. Then, the charged-particlebeam deflected by the deflector 849 deviates from the beam axis AX todeteriorate positional accuracy of the charged-particle beam on thewafer. Also, deflection efficiencies of the deflectors 840 and 849 onthe aperture plate 831 and the wafer become larger than those of FIG.61, thereby lengthening the setting time.

FIG. 63 is a chart of a temporal change in a driving voltage of adeflector for showing a settling time of the deflector. In FIG. 63, atime position ta indicates a settling time required for the device ofFIG. 61, and a time position tb indicates a settling time required forthe device of FIG. 62.

Accordingly, there is a need for a charged-particle-beam exposure deviceand a charged-particle-beam exposure method which can improve thepositional accuracy of the charged-particle beam on a wafer, and whichcan shorten the settling time required when there is a step change in adriving voltage of a deflector.

In the following, embodiments of an eighth principle of the presentinvention will be described with reference to the accompanying drawings.

FIG. 64 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a first embodiment ofthe eighth principle of the present invention. A charged-particle beam(e.g., electron beam) emitted from the charged-particle gun 810 exposesa resist layer on a wafer 811. The stencil mask 812 has a plurality ofhole patterns frequently used in exposure processes. Thecharged-particle beam passes through a selected hole pattern so that across section of the charged-particle beam is shaped into a desiredpattern. This pattern is converged and projected to the wafer 811.

A beam trajectory 813 shows an extent of the charged-particle beampassing through electromagnetic lenses 821 through 825, and is shownenlarged in a direction perpendicular to the beam axis AX. Theelectromagnetic lens 821 includes the electromagnetic lens 821A and theelectromagnetic lens 821B, and the aperture plate 830 is placed betweenthe electromagnetic lenses 821A and 821B. The charged-particle beamdeflected parallel to the beam axis AX by the electromagnetic lens 821Apasses through a square hole of the aperture plate 830 such that thecharged-particle beam has a cross-sectional size covering only one holepattern of the stencil mask 812. The electromagnetic lens 822 includesthe electromagnetic lens 822A and the electromagnetic lens 822B, and thestencil mask 812 is placed between the electromagnetic lenses 822A and822B. The charged-particle beam deflected parallel to the beam axis AXby the electromagnetic lens 822A passes through a selected hole patternof the stencil mask 812. The electromagnetic lenses 823 and 824 are usedfor a reduction projection of the charged-particle beam, and theaperture plate 831 having a round aperture is placed between theelectromagnetic lens 823 and the electromagnetic lens 824. Theelectromagnetic lens 825 is an objective lens, and converges thecharged-particle beam on the wafer 811.

A main deflector 832 and a sub-deflector 833 deflect thecharged-particle beam to a target position on the wafer 811.

The cross-over image CO1 of the gun cross over CO is positioned betweenthe electromagnetic lens 821B and the electromagnetic lens 822A. Thecross-over image CO2 of the gun cross over CO is positioned between theelectromagnetic lens 822B and the electromagnetic lens 823. Also, across-over image CO3 of the gun cross over CO is located between theelectromagnetic lens 823 and the electromagnetic lens 824.

In order to deflect the charged-particle beam from the beam axis AX to aselected hole pattern of the stencil mask 812, the deflector 840 isplaced between the electromagnetic lens 821B and the electromagneticlens 822A. Here, a center point of the deflector 840 is positioned at aposition of the cross-over image CO. In order to deflect thecharged-particle beam having passed through the electromagnetic lens822B back to the beam axis AX, deflectors 841 and 842 are situatedbetween the electromagnetic lens 822B and the electromagnetic lens 823.The deflector 842 is situated nearer to the electromagnetic lens 823.However, since the cross-over image CO2 is positioned only severalmillimeter from the top of the electromagnetic lens 823, a center pointof the deflector 842 cannot be located at a position of the cross-overimage CO2. Because of this reason, the deflector 841 is situated nearerto the electromagnetic lens 822B.

The aperture plate 831 is situated such that a center of the roundaperture coincides with a position of the cross-over image CO3.

Because of a variation in a thermal expansion due to ambient-temperaturechanges and a variation in the atmospheric pressure, the electromagneticlenses are subjected to varying stresses. Also, as electrodes of thecharged-particle gun 810 are worn over a long time, the positions of thecross-over images CO1 and CO2 vary slightly. Because of these factorsand deviations from design specifications, the charged-particle beamhaving passed through the electromagnetic lens 823 is displaced from thebeam axis AX. In order to correct this displacement, a correctiondeflector 843 is provided between the deflector 840 and electromagneticlens 822A, and a correction deflector 844 is provided between thedeflector 841 and the deflector 842.

An output of an amplifier 850 is connected to the deflector 840, and anoutput of an amplifier 851 is connected to the deflector 841 and thedeflector 842. Also, outputs of amplifiers 853 and 854 are connected tothe correction deflectors 843 and 844, respectively. The deflectors 840through 844 are static-charge-type deflectors, each having opposingelectrodes. The opposing electrodes receive voltages having the samemagnitude and a reversed phase. Since each of the deflectors 840 through844 generates only a small deflection angle, a trajectory of thecharged-particle beam keeps a linear relation with the voltage appliedto a deflector. Voltage ratios between the deflectors 840 through 844are kept constant irrespective of a position of a selected pattern ofthe stencil mask 812.

FIG. 65 is an illustrative drawing showing a configuration of thedeflectors 841, 842, and 844.

Each of the deflectors 841, 842, and 844 are comprised of eightelectrodes in order to have a uniform distribution of the electricfield. (The deflector 840 and the correction deflector 843 also have thesame configuration.) Because of these eight electrodes, the amplifier851 of FIG. 64 includes amplifiers 1011 through 1018. Outputs of theamplifiers 1011 through 1018 are connected to electrodes 911 through 918of the deflector 841, respectively, and are also connected to electrodes921 through 928 of the deflector 842, respectively.

The deflector 841 and the deflector 842 are supported by a supporter 860and a supporter 861, respectively. Center axes of the deflectors 841,842, and 844 are positioned at the beam axis AX. (The deflector 840 andthe correction deflector 843 of FIG. 64 also have the sameconfiguration.) Rotation errors of the deflectors 841 and 842 around thebeam axis AX are electrically corrected by applying a coordinatetransformation to signals suppled to the amplifiers 1011 through 1018.However, since the same output of the same amplifier is applied to arespective electrode of the deflector 841 and the deflector 842, theelectrical correction is effective only for one of the deflector 841 andthe deflector 842. In response, teeth 862 are formed on part of the sidesurface of the supporter 860, and a worm 863 is fitted to the teeth 862.The worm 863 has a wheel 864 attached thereto, and rotation of the wheel864 allows a mechanical correction of the deflector 841.

FIGS. 66A and 66B are illustrative drawings for explaining trajectoriesof the charged-particle beam deflected by the deflectors.

In FIG. 66A, the deflectors 841 through 843 receive a zero voltage. Whenthe charged-particle beam is deflected by the deflector 840, a linearlyapproximated trajectory 813D of the charged-particle beam is obtained asshown in FIG. 66A. Namely, since the center point of the deflector 840is positioned at the position of the cross-over image CO1, thecharged-particle beam deflected by the deflector 840 becomes parallel tothe beam axis AX after passing through the electromagnetic lens 822A.Also, after passing through the electromagnetic lens 822B, thecharged-particle beam reaches the position of the cross-over image CO2,and, then, reaches the position of the cross-over image CO3.

In FIG. 66B, voltages applied to the deflectors 840, 843, and 844 arezero. Also, it is assumed that a charged-particle beam is directedupward along the beam axis AX from a point below the aperture plate 831and that the charged-particle beam is deflected by the deflector 841 andthe deflector 842. In this case, a linearly approximated trajectory 813Eas shown in FIG. 66B is obtained. Here, a deflection by the deflector841 is set to such an amount that a dotted line running through pointsP3 and P4 and extended upstream runs through the position of thecross-over image CO2. If setting is made to satisfy this condition whenthe same voltage is applied to the deflector 841 and the deflector 842,this condition will be satisfied for any voltages as long as thesevoltages are within a range allowing the linear approximation. Thecharged-particle beam having passed through the electromagnetic lens822B is paralleled to the beam axis AX. After passing through theelectromagnetic lens 822A, the charged-particle beam runs through theposition of the cross-over image CO1.

Assume that when a voltage VM1 is applied to the deflector 840 in FIG.66A and a voltage VM2 is applied to the deflectors 841 and 842 in FIG.66B, a point P3 of FIG. 66A is at the same position as a point P3 ofFIG. 66B. This condition is satisfied even when the voltages VM1 and VM2are changed, as long as a ratio between VM1 and VM2 is kept constant.

When the voltage VM1 is applied to the deflector 840 and the voltage VM2is applied to the deflectors 841 and 842, a charged-particle beamdirected downward along the beam axis AX above the deflector 840 willhave a linearly approximated trajectory running through points P1, CO1,P2, and P3 of FIG. 66A and through points P4, P5, and P6 of FIG. 66B.

The deflectors 841 and 842 are designed such that when the same voltageis applied, the charged-particle beam is deflected as described above. Adeviation from the design specification can be corrected by adjusting aninterval between the deflector 841 and the deflector 842.

In FIG. 64, when there is no positional error of the cross-over imagesCO1 and CO2, changes in the voltages VM1 and VM2 will not bring about achange in the position of the charged-particle beam on the apertureplate 831 and the wafer 811 (the deflection efficiency is zero). On theother hand, changes in voltages VS1 and VS2 (shown in FIG. 64) result inthe position of the charged-particle beam being changed on the apertureplate 831 and the wafer 811. As for the deflectors 840 through 844, theyhave following characteristics.

(1) Even when the cross-over images CO1 and CO2 have positional errors,the deflection efficiency on the aperture plate 831 and the wafer 811 islarger for the correction deflectors 843 and 844 than for the deflectors840 through 842. Also, the correction deflectors 843 and 844 are usedfor correcting small errors. Thus, lengths of the correction deflectors843 and 844 along the beam axis AX can be set much shorter than those ofthe deflectors 840 through 842.

(2) The length of the correction deflector 843 along the beam axis AX ismuch shorter than that of the deflector 840, and the cross-over imageCO1 is distanced from the correction deflector 843. Thus, the deflector840 has much larger deflection efficiency on the stencil mask 812 thandoes the correction deflector 843. The fact that an effect of thecorrection deflector 843 on a beam position on the stencil mask 812 issmall is quite favorable.

Positional errors of the cross-over images CO1 and CO2 can be correctedby using the electromagnetic lens 821B, the correction deflector 843,and the correction deflector 844. This will be described below.

FIGS. 67A through 67C are illustrative drawings showing an extent of thecharged-particle beam passing through the electromagnetic lenses 821through 823 with an enlargement of this extent in a directionperpendicular to the beam axis AX. Beam extents 13F through 13H areshown in FIGS. 67A through 67C, respectively, when voltages applied tothe deflectors 840 through 844 are zero.

A current I passing through the aperture of the aperture plate 831 ismeasured by a Faraday cup 855 placed under the aperture.

FIGS. 67A and 67C show cases when the position of the cross-over imageCO1 is displaced from the center point of the deflector 840. In thesecases, when the deflector 840 deflects the charged-particle beam whileno voltage is applied to the deflectors 841 through 844, the current Ichanges according to the deflection amount. Then, a current applied tothe electromagnetic lens 821 (electromagnetic lens 821B of FIG. 64 to beexact) is changed to shift the focusing thereof, so that the position ofthe cross-over image CO1 is changed along the beam axis AX. When theposition of the cross-over image CO1 coincides with the center point ofthe deflector 840 as shown in FIG. 67B, a change in the deflectionamount of the deflector 840 will not affect the current I.

In order to correct the position of the cross-over image CO1, voltagesapplied to the deflectors 841 through 844 are set to zero, and thefocusing of the electromagnetic lens 821 is changed step by step. Foreach step of the focusing, a change in the current I in response to achange in the deflection amount of the deflector 840 is measured. Then,the focusing A1 of the electromagnetic lens 821 when the change in thecurrent I is the smallest is obtained.

In order to correct the position of the cross-over image CO2, voltagesapplied to the deflectors 840, 843, and 844 are set to zero, and thefocusing of the electromagnetic lens 821 is changed step by step. Foreach step of the focusing, a change in the current I in response tochanges in the deflection amounts of the deflectors 841 and 842 ismeasured. Then, the focusing A2 of the electromagnetic lens 821 when thechange in the current I is the smallest is obtained.

When the focusing of the electromagnetic lens 821 is A1, the cross-overimage CO1 does not have a positional error, but the cross-over image CO2does. On the other hand, when the focusing of the electromagnetic lens821 is A2, the cross-over image CO1 has a positional error, but thecross-over image CO2 does not. That is, desirable focusing of theelectromagnetic lens 821 is not A1 nor A2. Assuming that the desirablefocusing is L, the focusing of the electromagnetic lens 821 is set to L.

Then, voltages applied to the deflectors 841, 842, and 844 are set tozero. The voltage VS1 K1 times as large as the voltage VM1 for thedeflector 840 is applied to the correction deflector 843. Then, thefactor K1 is changed step by step. For each step of the factor K1, achange in the current I in response to a change in the deflection amountof the deflector 840 is measured. The factor K1 for the smallest changein the current I is then determined. Then, voltages applied to thedeflectors 840 and 843 are set to zero. The voltage VS2 K2 times aslarge as the voltages VM2 for the deflectors 841 and 842 is applied tothe correction deflector 844. Then, the factor K2 is changed step bystep. For each step of the factor K2, a change in the current I inresponse to changes in the deflection amounts of the deflectors 841 and842 is measured. The factor K2 for the smallest change in the current Iis then determined. Based on the factors K1 and K2, a ratio M:N(=VS1:VS2) is calculated. The ratio M:N is constant irrespective of thebeam position on the stencil mask 812.

An analysis of a relation between the desirable focusing L of theelectromagnetic lens 821 and the ratio M:N will be provided below. IfM/(M+N) is larger than N/(M+N), the focusing L is expected to be nearerto A1 than to A2. On the other hand, if M/(M+N) is smaller than N/(M+N),the focusing L is expected to be nearer to A2 than to A1.

Voltages applied to the deflectors 841 through 844 are set to zero, andthe focusing of the electromagnetic lens 821 is changed step by step.For each step of the focusing, a change in the current I in response toa change in the deflection amount of the deflector 840 is measured.Then, the focusing A1 of the electromagnetic lens 821 when the change inthe current I is the smallest is obtained.

Voltages applied to the deflectors 840, 843, and 844 are set to zero,and the focusing of the electromagnetic lens 821 is changed step bystep. For each step of the focusing, a change in the current I inresponse to changes in the deflection amounts of the deflectors 841 and842 is measured. Then, the focusing A2 of the electromagnetic lens 821when the change in the current I is the smallest is obtained.

Then, the desirable focusing L is determined as:

    L=(M•A1+N•A2)/(M+N)                            (22)

The ratio M:N has an initial value 1:1, for example, and the focusing Lis obtained for this initial value by using the equation (22). Then, theratio M:N is obtained as described above by using the focusing L. Such aprocess is carried out one or more times to move the ratio M:N closer toan optimal ratio.

FIG. 68 is a flowchart of the above-described process of determining thefocusing A1 to correct the position of the cross-over image CO. Theprocess of determining the focusing A2 is almost the same as the processof determining the focusing A1 except for the selection of thedeflectors, and a flowchart thereof will be omitted.

At a step S201, voltages applied to irrelevant deflectors are set tozero.

At a step S202, the focusing of the electromagnetic lens 821 is changedstep by step, and a change in the current I in response to a change inthe deflection amount of a relevant deflector is measured for each stepof the focusing.

At a step S203, the focusing A1 of the electromagnetic lens 821 for thesmallest change in the current I is obtained. This ends the procedure.

FIG. 69 is a flowchart of the above-described process of obtaining thedesirable focusing L and the optimal value of the ratio M:N.

At a step S211, the focusing A1 and the focusing A2 are obtained.

At a step S212, the ratio M:N is set to an initial value.

At a step 5213, the focusing L is obtained by using the equation (22).

At a step S214, the ratio M:N is obtained as described above by usingthe focusing L.

At a step S215, a check is made whether the ratio M:N is close enough toan optimal ratio. If it is not, the procedure goes back to the step S213to repeat the steps S213 through S215. If the ratio M:N is close enoughto an optimal ratio, the procedure ends.

Alternately, the ratio M:N may be obtained as follows.

When the Faraday cup 855 is removed, a position P of thecharged-particle beam on the wafer 811 varies depending on the voltagesVS1 and VS2. First, the ratio M:N is set to 1:1, for example, and thefocusing L is obtained by using the equation (22). Then, an equationrepresenting a relation between the voltages VS1 and VS2, the current I,and the position P is obtained experimentally. Then, the ratio M:N whenthe current I is maximum and the position P is on the beam axis AX isobtained. Such a process is carried out one or more times to make theratio M:N closer to an optimal ratio.

The determination of the factors K1 and K2 and the focusing L asdescribed above is carried out when the charged-particle-beam exposuredevice is calibrated.

In the first embodiment of the eighth principle of the presentinvention, not only the correction deflectors 843 and 844 but also theelectromagnetic lens 821B are corrected in relation with the current I,so that the correction of the device is precise.

A relation between this correction and the settling time when thevoltages VM1 and VM2 show a step change will be explained below.

In selecting a hole pattern of the stencil mask 812, the voltages VM1and VM2 are changed by a given step voltage. A precision required forpositioning the charged-particle beam on the wafer 811 is within a rangeof 0.01 μm. As previously described, the charged-particle beam should beblanked out until this level of precision is guaranteed. Since thecharged-particle beam is continuously emitted, the blanking of the beamis carried out by using the aperture plate 831 and a deflector placedabove the aperture plate 831. Even if the step change is the samebetween the voltages VM1 and VM2, the larger the changes in the positionof the charged-particle beam (i.e., deflection efficiency) on the wafer811 with respect to changes in the voltages VM1 and VM2, the longer thesettling time (blanking time) is.

Without the correction described above, the deflection efficiency islarge so that the settling time is long. FIG. 70 is a chart showing ashortening of the settling time because of the correction. Without thecorrection, the settling time of the voltage VM1, for example, islengthy as shown by t2 in FIG. 70. When the correction is conducted, thedeflection efficiency is decreased, so that the settling time becomesshorter as shown by t1 in FIG. 70. The settling time t1 in this case maybe 500 ns, for example. In this manner, throughput of the exposureprocess is enhanced. Since the correction is accurate as describedabove, the reduction in the settling time is significant.

FIG. 71 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a second embodimentof the eighth principle of the present invention.

In the device of FIG. 71, the correction deflector 843 is placed betweenthe electromagnetic lens 821B and the deflector 840. Except for thischange, the device of FIG. 71 is the same as that of FIG. 64.

In the second embodiment of the eighth principle, the characteristics(1) and (2) described in the first embodiment of the eighth principleare upheld. Thus, what has been described for the first embodiment ofthe eighth principle can also be applied to the configuration of thesecond embodiment. To avoid repetition, a description of the secondembodiment the same as that of the first embodiment will be omitted.

FIG. 72 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a third embodiment ofthe eighth principle of the present invention.

In the device of FIG. 72, deflectors similar to the deflectors 841, 842,and 844 of FIG. 64 are arranged to replace the deflectors 840 and 843 ofFIG. 64. Namely, deflectors 1141, 1142, and 1144 are situated betweenthe electromagnetic lens 821B and the electromagnetic lens 822A in amirror-image configuration to the deflectors 841, 842, and 844. Avoltage VM1 output from an amplifier 1151 is applied to the deflectors1141 and 1142, and a voltage VS1 output from an amplifier 1154 isapplied to the correction deflector 1144. The cross-over image CO1 ispositioned between the electromagnetic lens 821B and a contour point ofthe deflector 1142. Other elements have the same configuration as thoseof FIG. 64.

FIGS. 73A and 73B are illustrative drawings for explaining trajectoriesof the charged-particle beam deflected by the deflectors. FIGS. 73A and73B correspond to FIGS. 66A and 66B, respectively.

In FIG. 73A, the deflectors 1144, 841, 842, and 844 receive a zerovoltage. When the charged-particle beam running downward along the beamaxis AX is deflected by the deflectors 1142 and 1141, a linearlyapproximated trajectory 813I of the charged-particle beam is obtained asshown in FIG. 73A.

In FIG. 73B, voltages applied to the deflectors 1141, 1142, 1144, and844 are zero. Also, it is assumed that a charged-particle beam isdirected upward along the beam axis AX from a point below the apertureplate 831 and that the charged-particle beam is deflected by thedeflector 841 and the deflector 842. In this case, a linearlyapproximated trajectory 813J as shown in FIG. 73B is obtained.

Assume that when a voltage VM1 is applied to the deflectors 1141 and1142 in FIG. 73A and a voltage VM2 is applied to the deflectors 841 and842 in FIG. 73B, a point P3 of FIG. 73A is at the same position as apoint P3 of FIG. 73B. This condition is satisfied even when the voltagesVM1 and VM2 are changed, as long as a ratio between VM1 and VM2 is keptconstant.

When the voltage VM1 is applied to the deflectors 1141 and 1142 and thevoltage VM2 is applied to the deflectors 841 and 842, a charged-particlebeam directed downward along the beam axis AX above the deflector 1142will have a linearly approximated trajectory running through points P1,P5A, P4A, P2 and P3 of FIG. 73A and through points P4, P5, and P6 ofFIG. 73B.

Other than what has been described above, the same thing as the firstembodiment can be applied to the third embodiment of the eighthprinciple of the present invention.

FIG. 74 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a fourth embodimentof the eighth principle of the present invention.

The configuration of FIG. 74 differs from that of FIG. 64 only in thatthe amplifier 850 of FIG. 64 is removed. Since the voltage applied tothe deflector 840 is in proportion to the voltage applied to thedeflectors 841 and 842, the deflector 840 in FIG. 74 is designed suchthat this proportion factor is equal to 1. Then, the voltage VM2 outputfrom the amplifier 851 is applied to the deflector 840. One of thedeflectors 840, 841, and 842 allows an electrical adjustment of arotation angle around the beam axis AX. The other two of them aremechanically adjustable in the same manner as shown in FIG. 65.

In the fourth embodiment of the eighth principle of the presentinvention, the voltage VM2 output from the amplifier 851 is applied tothe deflectors 841, 842, and 840. Thus, when the voltage VM2 of theamplifier 851 has a step change, transient characteristics of theelectric fields generated by the deflector 841, 842, and 840 become thesame with each other, so that determination of the settling time becomeseasier. If different amplifiers are used for the deflector 840 and thedeflectors 841 and 842, transient characteristics of the deflectors aredifferent. In this case, the settling time should be determined byselecting the longest settling time, thereby complicating a process ofdetermining the settling time. In the fourth embodiment of the eighthprinciple, it is easier to determine the settling time without goingthrough a complicated process.

FIG. 75 is an illustrative drawing of a configuration of acharged-particle-beam exposure device according to a fifth embodiment ofthe eighth principle of the present invention.

As described in the first embodiment of the eighth principle, atrajectory of the charged-particle beam can be expressed by a linearapproximation with respect to the voltages applied to the deflectors 840through 843. This is because the deflection amount is small. Secondorders of the applied voltages can be a cause of an aberration, but doesnot have any effect on the trajectory of the charged-particle beam alongthe beam axis. However, third orders of the applied voltages affects thetrajectory of the charged-particle beam along the beam axis. Thus, whenthe applied voltages have step changes, a position of thecharged-particle beam at the aperture plate 831 fluctuates. In thiscase, the amount of current passing through the aperture plate 831 isgenerally proportional to the third power of the applied voltage.Although a fluctuation in a position of the charged-particle beam on thewafer 811 can be ignored, the fluctuation of the current amount cannot.Therefore, there is a need to take into account the third orders of theapplied voltages with respect to the settling time.

Assume that a precision required for positioning the charged-particlebeam on the wafer 811 is 0.01 μm, that a maximum amount of deflection(distance from the beam axis AX) of the charged-particle beam on thestencil mask 812 is 5 mm, and that a reduction rate of a hole pattern ofthe stencil mask 812 when projected on the wafer 811 is 1/100. In thiscase, a 5-mm step change at the stencil mask 812 corresponds to a 50-μmstep change on the wafer 811. Thus, in order to keep a step change onthe wafer 811 within a range of 0.01 μm, a difference dV between thevoltage VM1 and a stable voltage V0 should satisfy the followinginequality:

    dV/V0≦0.01/50=1/5000                                (23)

FIG. 76A is a chart for explaining a relation between the difference dVand the settling time. In the figure, the settling time is t1, at whichdV/V should be equal to or smaller than 1/5000. In practice, t1 is about500 nsec.

If a temporal change of VM1 is approximated to by

    VM1(t)=V0{1-exp(-t/a)},                                    (24)

and dV/V0 becomes equal to 1/5000 within 500 nsec, a constant a is 60.3nsec.

A current I(t) passing through the aperture of the aperture plate 831 isproportional to {VM1(t)}³. Thus, I(t) is approximated to by

    I(t)=I0{1-exp(-t/a)}.sup.3,                                (24)

Assume that, in order to have an accurate exposure amount, thecharged-particle beam should be blanked out until the current amount ofthe charged-particle beam on the wafer 811 reaches approximately 99% ofthe stable current amount. In consideration of the reduction rate of1/100, a difference dI0 between the current I(t) and a stable current I0should satisfy the following inequality:

    dI0/I0≦(1/100)(1/100)=1/10000                       (25)

FIG. 76B is a chart for explaining a relation between the difference dI0and the settling time. In the figure, the settling time is t3, at whichdI0/I0 should be equal to or smaller than 1/10000. In practice, t3 isabout 620 nsec. In this case, the settling time is determined not by theequation (23) but by the equation (25).

The settling time t3 of FIG. 76B is compared with a settling time t2 ofFIG. 76A, for which no correction described in the first embodiment ofthe eighth principle is carried out. Because of no correction, thefluctuation in the position of the charged-particle beam at the apertureplate 831 is large so that the settling time t2 is longer than thesettling time t3.

The deflection efficiencies on the aperture plate 831 and the wafer 811are greater for the correction deflector 843 than for the deflector 840.Since the correction deflector 843 is used for correction of smallerrors, the voltage VS1 of the amplifier 853 is much smaller than thevoltage VM1 of the amplifier 850. Thus, the voltage VS1 output from theamplifier 853 has a settling time much shorter than that of the voltageVM1. FIG. 76C is a chart showing a change of the voltage VS1 and asettling time t6 thereof. Because t6 is much shorter than t1, thecorrection of the fluctuation of the charged-particle-beam position onthe aperture plate 831 can be carried out by using the correctiondeflector 843.

In the device of FIG. 75, the correction deflector 843 is used forcorrecting the fluctuation in the position of the charged-particle beamat the aperture plate 831 when the voltages applied to the deflectors840 through 844 have step changes to cause the fluctuation through thethird order of the applied voltages. The configuration of FIG. 75includes elements 870 through 884 in addition to the configuration ofFIG. 64.

Data D1 for selecting a hole pattern of the stencil mask 812 is storedin a data generating unit 870. This pattern-selection data D1sequentially read from the data generating unit 870 is converted toanalog data by a D/A converter 871, and, then, amplified by theamplifier 850 to become the voltage VM1 applied to the deflector 840.The voltage VS1 generated through a D/A conversion by a D/A converter872 and the amplification by the amplifier 853 is supplied to thecorrection deflector 843. The D/A converter 872 receives an output of anadder 873 adding correction values D2 and D3 together. The correctionvalue D2 is equal to K1•D1, where K1 is the proportion factor previouslydescribed.

When creating a correction value for the correction deflector 843, thecorrection value D3 is first set to zero. The pattern-selection data D1is changed by a step, and a value proportional to the current I passingthrough the aperture of the aperture plate 831 is detected by ascattered-particle detector 874. A detected signal is amplified by anamplifier 875 and converted to a digital value SE by a D/A converter876. The digital value SE is provided for a control circuit 877. Sincethe deflectors 841 through 843 receive voltages proportional to that ofdeflector 840, the voltages input to the deflectors 841 through 843 havestep changes as does the voltage applied to the deflector 840.

At a time when the step change of the pattern-selection data D1 starts,a load signal supplied from the data generating unit 870 to aload-control-input node L of a counter 878 is activated. Thepattern-selection data D1 is supplied to a data-input node D of thecounter 878. Immediately after these operations, the data generatingunit 870 turns a start signal ST to a high level to open an AND gate879. Then, a clock CLK from a clock generator 880 is supplied to aclock-input node of the counter 878 via the AND gate 879. A countsupplied from a data-output node Q of the counter 878 serves as anaddress of a memory 881, and the control circuit 877 writes thescattered-particle amount (digital value) SE in this address of thememory 881. The writing of the data is carried out from data D1corresponding to each hole pattern of the stencil mask 812.

A memory 882 stores the correction value D3 which maximizes thescattered-particle amount SE for each data D1 corresponding to arespective hole pattern of the stencil mask 812. The correction value D3is obtained as follows.

The correction value D3 is changed for given pattern-selection data D1and given scattered-particle amount SE without correction. Then, thescattered-particle amount SE is measured for each correction value D3 toobtain a function of D3 for representing the scattered-particle amountSE. Then, the correction value D3 for the maximum scattered-particleamount SE is determined. The same procedure is conducted for a pluralityof scattered-particle amounts SE without correction. Then, thecorrection value D3 for every scattered-particle amount SE withoutcorrection is obtained. The same procedure is carried out for each dataD1 corresponding to a respective hole pattern of the stencil mask 812.

The correction values D3(D1, SE) (function of the data D1 and thescattered-particle amount SE) thus obtained are supplied to the controlcircuit 877. The control circuit 877 provides the memory 882 with anaddress (D1, SE) via a selector 883 to write a correction value D3 at anindicated address.

At a time of exposure, an output of the memory 881 instead of an outputof D/A converter 876 is used. This is because the output of the D/Aconverter 876 obtained from the output of scattered-particle detector874 varies depending on a surface structure of the wafer 811. Namely, itis preferable to use the scattered-particle amounts SE detected for aflat surface of the wafer 811 and stored in the memory 881.

At a time of exposure, the memory 881 and the memory 882 are set to aread state, and the selector 883 is set to select an address from thememory 881. When the data D1 is changed by a step to select a holepattern of the stencil mask 812, the load-control-input node L of thecounter 878 is activated so that the counter 878 reads thepattern-selection data D1. Immediately after these operations, the startsignal ST is turned to the high level, so that the clock CLK from theclock generator 880 is counted by the counter 878. A count obtained bythe counter 878 is used for indicating an address of the memory 881 toread the scattered-particle amount SE from the memory 881. Thisscattered-particle amount SE is provided for the memory 882 as anaddress, so that the correction value D3 is read from the memory 882 tobe supplied to the adder 873.

FIG. 76D is a chart showing an example of the correction value D3 forgiven pattern-selection data D1. Use of the correction value D3 as shownin FIG. 76D results in the current I passing through the aperture beingchanged as shown by a dotted line in FIG. 76B. Thus, the settling timeis shortened from t3 to t5, which is shorter than t1 of FIG. 76A. Then,the settling time required for selecting a hole pattern of the stencilmask 812 becomes t1, thereby enhancing throughput of the exposure.

It is possible for the counter 878 to directly provide an address of thememory 882. Since the memory 881 storing the scattered-particle amountsSE is used in the fifth embodiment of the eighth principle, a relationbetween the scattered-particle amounts SE and the correction values D3can be inspected at any time. Thus, it is easier to modify thecorrection values D3 to more appropriate values.

Further, the present invention is not limited to these embodiments, butvariations and modifications may be made without departing from thescope of the present invention.

What is claimed is:
 1. A method of exposing a wafer to acharged-particle beam by directing to said wafer said charged-particlebeam deflected by a deflector, said method comprising the steps of:a)positioning a position-detection mark at predetermined locations, saidposition-detection mark including heavy metal buried in a substratehaving lower reflectivity than said heavy metal, said heavy metal andsaid substrate having a unitary flat surface; and b) detecting positionsof said position-detection mark by using said charged-particle beam. 2.The method as claimed in claim 1, further comprising a step ofcalibrating a deflection of said charged-particle beam by usingdeflection-efficiency-correction coefficients and adeflection-distortion map obtained based on said positions of saidposition-detection mark, said deflection-efficiency-correctioncoefficients being used for correcting linear factors of said deflector,said deflection-distortion map being used for correcting a distortion ofsaid deflector.
 3. The method as claimed in claim 2, further comprisingthe steps of:positioning at least one positioning mark on said wafer ata predetermined location through stage movement; detecting a position ofsaid at least one positioning mark by using said charged-particle beam;and exposing a calibrated charged-particle beam on said wafer based onsaid position of said at least one positioning mark.
 4. The method asclaimed in claim 3, wherein said predetermined location is at a centeraxis of an optical system of said charged-particle beam.
 5. The methodas claimed in claim 1, further comprising a step of calibrating adeflection of said charged-particle beam by using adeflection-distortion map obtained based on said positions of saidposition-detection mark, said deflection-distortion map being used forcorrecting a distortion of said deflector.
 6. The method as claimed inclaim 5, further comprising the steps of:positioning at least onepositioning mark on said wafer at a predetermined location through stagemovement; detecting a position of said at least one positioning mark byusing said charged-particle beam; obtainingdeflection-efficiency-correction coefficients based on said at least onepositioning mark, said deflection-efficiency-correction coefficientsbeing used for correcting linear factors of said deflector; calibratinga deflection of said charged-particle beam based on correctdeflection-efficiency-correction coefficients obtained by adding apredetermined displacement to said deflection-efficiency-correctioncoefficients; and exposing a calibrated charged-particle beam on saidwafer based on said position of said at least one positioning mark. 7.The method as claimed in claim 5, further comprising the stepsof:positioning at least one positioning mark on said wafer at apredetermined location through stage movement; detecting a position ofsaid at least one positioning mark by using said charged-particle beam;obtaining deflection-efficiency-correction coefficients by using a markfor adjusting said charged-particle beam, saiddeflection-efficiency-correction coefficients being used for correctinglinear factors of said deflector; calibrating a deflection of saidcharged-particle beam based on correct deflection-efficiency-correctioncoefficients obtained by adding a predetermined displacement to saiddeflection-efficiency-correction coefficients; and exposing a calibratedcharged-particle beam on said wafer based on said position of said atleast one positioning mark.
 8. The method as claimed in claim 1, whereinsaid heavy metal comprises one of gold, tantalum, and a tungsten, andsaid substrate comprises silicon.
 9. The method as claimed in claim 1,wherein said unitary flat surface comprises a surface polished by achemical-mechanical polishing method.
 10. A device for exposing a waferto a charged-particle beam by directing to said wafer saidcharged-particle beam deflected by a deflector, said device comprising:awafer stage supporting said wafer to move said wafer; and aposition-detection mark provided on said wafer stage, said positiondetection mark including heavy metal buried in a substrate having lowerreflectivity than said heavy metal, said heavy metal and said substratehaving a unitary flat surface.
 11. The device as claimed in claim 10,further comprising:first means for positioning said position-detectionmark at predetermined locations through movement of said wafer stage;second means for detecting positions of said position-detection mark byusing said charged-particle beam; and third means for calibrating adeflection of said charged-particle beam by usingdeflection-efficiency-correction coefficients and adeflection-distortion map obtained based on said positions of saidposition-detection mark, said deflection-efficiency-correctioncoefficients being used for correcting linear factors of said deflector,said deflection-distortion map being used for correcting a distortion ofsaid deflector.
 12. The device as claimed in claim 11, furthercomprising:means for positioning at least one positioning mark on saidwafer at a predetermined location through movement of said wafer stage;means for detecting a position of said at least one positioning mark byusing said charged-particle beam; and means for exposing a calibratedcharged-particle beam on said wafer based on said position of said atleast one positioning mark.
 13. The device as claimed in claim 12,wherein said predetermined location is at a center axis of an opticalsystem of said charged-particle beam.
 14. The device as claimed in claim10, further comprising:first means for positioning saidposition-detection mark at predetermined locations through movement ofsaid wafer stage; second means for detecting positions of saidposition-detection mark by using said charged-particle beam; and thirdmeans for calibrating a deflection of said charged-particle beam byusing a deflection-distortion map obtained based on said positions ofsaid position-detection mark, said deflection-distortion map being usedfor correcting a distortion of said deflector.
 15. The device as claimedin claim 14, further comprising:means for positioning at least onepositioning mark on said wafer at a predetermined location throughmovement of said wafer stage; means for detecting a position of said atleast one positioning mark by using said charged-particle beam; meansfor obtaining deflection-efficiency-correction coefficients based onsaid at least one positioning mark, saiddeflection-efficiency-correction coefficients being used for correctinglinear factors of said deflector; means for calibrating a deflection ofsaid charged-particle beam based on correctdeflection-efficiency-correction coefficients obtained by adding apredetermined displacement to said deflection-efficiency-correctioncoefficients; and means for exposing a calibrated charged-particle beamon said wafer based on said position of said at least one positioningmark.
 16. The device as claimed in claim 14, further comprising:meansfor positioning at least one positioning mark on said wafer at apredetermined location through movement of said wafer stage; means fordetecting a position of said at least one positioning mark by using saidcharged-particle beam; means for obtainingdeflection-efficiency-correction coefficients by using a mark foradjusting said charged-particle beam, saiddeflection-efficiency-correction coefficients being used for correctinglinear factors of said deflector; means for calibrating a deflection ofsaid charged-particle beam based on correctdeflection-efficiency-correction coefficients obtained by adding apredetermined displacement to said deflection-efficiency-correctioncoefficients; and means for exposing a calibrated charged-particle beamon said wafer based on said position of said at least one positioningmark.
 17. The device as claimed in claim 10, wherein said heavy metalcomprises one of gold, tantalum, and a tungsten, and said substratecomprises silicon.
 18. The method as claimed in claim 10, wherein saidunitary flat surface comprises a surface polished by achemical-mechanical polishing method.